Modified Plant Defensins Useful as Anti-Pathogenic Agents

ABSTRACT

This disclosure relates generally to the field of anti-pathogenic agents, including a modified defensin molecule with anti-pathogen activity. Genetically modified plants and their progeny or parts expressing or containing the modified defensin and anti-pathogen compositions for use in horticulture and agriculture and as animal and human medicaments are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser. No. 13/983,941, filed Oct. 28, 2013, which is a U.S. National Stage application filed under 35 U.S.C. §371 of International Application No. PCT/AU2012/000112, filed Feb. 7, 2012, which claims the benefit of U.S. Provisional Application No. 61/440,309, filed Feb. 7, 2011. Each of these applications is incorporated by reference in its entirety herein.

FIELD

This disclosure relates generally to the field of anti-pathogenic agents, including a modified defensin molecule with anti-pathogen activity. Genetically modified plants and their progeny or parts expressing or containing the modified defensin and anti-pathogen compositions for use in horticulture and agriculture and as animal and human medicaments are also provided.

BACKGROUND

Bibliographic details of the publications referred to by author in this specification are collected alphabetically at the end of the description.

Reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that this prior art forms part of the common general knowledge in any country.

One of the major difficulties facing the horticultural and agricultural industries is the control of infestation and resulting damage by pathogens such as fungal pathogens. Plant pathogens account for millions of tonnes of lost production on an annual basis. Although fungicides and other anti-pathogenic chemical agents have been successfully employed, there is a range of environmental and regulatory concerns with the continued use of chemical agents to control plant pests. Furthermore, the increasing use of chemical pesticides is providing selective pressure for the emergence of resistance in populations of pests. There is clearly a need to develop alternative mechanisms of inducing resistance in plants to pathogens such as fungi, insects, microorganisms, nematodes, arachnids, protozoa and viruses.

The plant innate immune system comprises both constitutive or pre-formed and inducible components. Pre-formed immunity includes various physical barriers such as wax layers on leaves and rigid cell walls as well as expression of various antimicrobial proteins (Nurnberger et al. (2004) Immunol Rev 198:249-266). The inducible response can include fortification of the cell wall (Showalter (1993) Plant Cell 5(1):9-23) as well as up-regulation of secondary metabolites (Metlen et al. (2009) Plant Cell Environ 32(6):641-653) and antimicrobial proteins (Berrocal-Lobo et al. (2002) Plant Physiol 128(3):951-961; Li and Asiegbu (2004) J Plant Res 117(2):155-162) which occurs in response to various biotic and abiotic stimuli. These responses can occur locally at the site of infection or in distant, uninfected parts of the plant to produce a systemic response. Inducible immunity can also occur via a gene-for-gene response whereby pathogen-associated molecular patterns (PAMPS) are recognized by specific pattern recognition receptors (PRRs) resulting in a hypersensitive response that prevents further spread of the pathogen (see Jones and Dangl (2006) Nature 444(7117):323-329).

Small, disulfide-rich proteins play a large role in both the constitutive and inducible aspects of plant immunity. They can be categorized into families based on their cysteine arrangements and include the thionins, snakins, thaumatin-like proteins, havein- and knottin-type proteins, lipid transfer proteins and cyclotides as well as defensins.

Plant defensins are small (45-54 amino acids), basic proteins with four to five disulfide bonds (Janssen et al. (2003) Biochemistry 42(27):8214-8222). They share a common disulfide bonding pattern and a common structural fold, in which a triple-stranded, antiparallel β-sheet is tethered to an α-helix by three disulfide bonds, forming a cysteine-stabilized αβ motif (CSαβ [see FIG. 1]). A fourth disulfide bond also joins the N- and C-termini leading to an extremely stable structure. A variety of functions have been attributed to defensins, including anti-bacterial activity, protein synthesis inhibition and α-amylase and protease inhibition (Colilla et al. (1990) FEBS Lett 270(1-2):191-194; Bloch and Richardson (1991) FEBS Lett 279(1):101-104). Plant defensins have been expressed in transgenic plants, resulting in increased resistance to target pathogens. For example, potatoes expressing the alfalfa defensin (MsDef1, previously known as alfAFP) showed significant resistance against the fungal pathogen Verticillium dahliae compared to non-transformed controls (Gao et al. (2000) Nat Biotechnol 18(121:1307-1310). Expression of a Dahlia defensin (DmAMP1) in rice was sufficient to provide protection against two major rice pathogens, Magnaporthe oryzae and Rhizoctonia solani (Jha et al. (2009) Transgenic Res 18(11:59-69).

Despite their conserved structure, plant defensins share very little sequence identity, with only the eight cysteine residues completely conserved. The cysteine residues are commonly referred to as “invariant cysteine residues”, as their presence and location are conserved amongst defensins. Based on sequence similarity, plant defensins can be categorized into different groups (see FIG. 2). Within each group, sequence homology is relatively high whereas inter-group amino acid similarity is low. The anti-fungal defensins from distinct groups appear to act via different mechanisms.

Plant defensins can be divided into two major classes. Class I defensins consist of an endoplasmic reticulum (ER) signal sequence followed by a mature defensin domain. Class II defensins are produced as larger precursors with C-terminal pro-domains or pro-peptides (CTPPs) of about 33 amino acids. Most of the Class II defensins identified to date have been found in solanaceous plant species. An alignment of Class II solanaceous defensins is provided in FIG. 3. NsD1 and NsD2 referred to in FIG. 3 represent novel defensins identified in accordance with the present disclosure. Their inclusion in FIG. 3 is not to imply they form part of the prior art.

Class II solanaceous defensins display anti-fungal activity and are expressed in floral tissues. They include NaD1, which is expressed in high concentrations in the flowers of ornamental tobacco Nicotiana alata (Lay et al. (2003) Plant Physiol 131(3):1283-1293). NaD1 is the only Class II solanaceous defensin for which the mechanism of anti-fungal activity has been investigated. The activity of this peptide involves binding to the cell wall, permeabilization of the plasma membrane and entry of the peptide into the cytoplasm of the hyphae (van der Weerden et al. (2008) J Biol Chem 283(21):14445-14452). Unlike many other defensins, NaD1 appears to be specific for filamentous fungi and has no effect on the growth of yeast, bacteria or mammalian cells.

Expression of NaD1 in cotton enhances the resistance to the fungal pathogens Fusarium oxysporum fsp. vasinfectum and Verticillium dahliae. Under field conditions, plants expressing NaD1 were twice as likely to survive as untransformed control plants and the lint yield per hectare was doubled. Despite this, there was still a significant level of disease in the NaD1-expressing plants.

The structure of defensins consists of seven ‘loops’, defined as the regions between cysteine residues. Loop 1 encompasses the first β-strand (1A) as well as most of the flexible region that connects this β-strand to the α-helix (1B) between the first two invariant cysteine residues. FIG. 5 shows the loop structure of NaD1 including the conserved cysteine residues. Loops 2, 3 and the beginning of 4 (4A) make up the α-helix, while the remaining loops (4B-7) make up β-strands 2 and 3 and the flexible region that connects them (β-hairpin region). This hairpin region of plant defensins forms a γ-core motif that is found in many anti-microbial peptides of diverse classes (Yount and Yeaman (2005) Protein Pept Lett 12(1):49-67).

This β-hairpin region appears to be essential for the biological activity of plant defensins. Mutations in this region of the radish defensin RsAFP2 (See FIG. 2) generally had a negative impact on its anti-fungal activity. In fact, eight out of the twelve residues identified as essential for anti-fungal activity are located in this region (De Samblanx et al. (1997) J Biol Chem 272(2):1171-1179). Furthermore, a chemically synthesized peptide corresponding to this region of the molecule also has anti-fungal activity on its own (Schaaper et al. (2001) J. Pept. Res. 57(5):409-418). In a separate study, the six residues located in loop 5 of VrD2, a defensin from Vigna radiata, were shown to be essential for its α-amylase inhibitory activity (Lin et al. (2007) Proteins 68(2):530-540). A third study investigated the activity of chimeric proteins containing regions from a defensin with anti-fungal activity (MsDef1) and one without (MtDef2). Chimeric defensins that contained the β2-β3 hairpin region of MsDef1 had almost the same activity as the full MsDef1 protein and chimeric defensins that contained this region from MtDef2 had no activity (Spelbrink et al. (2004) Plant Physiol 135(4):2055-2067).

A flexible loop connecting the first β-strand and the α-helix located adjacent and N-terminal of the second invariant cysteine residue (Loop 1B) has been reported to play a minor role in the anti-fungal activity in some defensins when associated as a patch with residues from Loop5. A mutagenesis study of RsAFP2 identified two amino acids important for activity that were located in this region (De Samblanx et al, 1997 supra). However, when this region of the anti-fungal defensin MsDef1 was replaced with the corresponding region from the non-anti-fungal defensin, there was only a modest change in anti-fungal activity (Spelbrink et al, 2004 supra).

Class II solanaceous defensins have variable degrees of activity against fungi. Some Class I defensins exhibit very low anti-fungal activity. Attempts to modify the defensins to improve and broaden their anti-pathogen activity have hitherto been largely unsuccessful. Development of resistance to some defensins is also a potential problem. There is a need to develop protocols to manipulate the level and spectrum of anti-pathogen activity of defensins. The creation of a range of novel defensins with antipathogen activity also facilitates combating the development of resistance.

SUMMARY

Throughout this specification, unless the context requires otherwise, the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element or integer or method step or group of elements or integers or method steps but not the exclusion of any other element or integer or method step or group of elements or integers or method steps.

As used in the subject specification, the singular forms “a”, “an” and “the” include plural aspects unless the context clearly dictates otherwise. Thus, for example, reference to “a defensin” includes a single defensin, as well as two or more defensins; reference to “an amino acid, substitution, addition and/or deletion” includes a single amino acid, substitution, addition and/or deletion, as well as two or more amino acids, substitutions, additions and/or deletions; reference to “the aspect” includes a single aspect, as well as two or more aspects as taught in the specification; and so forth.

Nucleotide and amino acid sequences are referred to by a sequence identifier number (SEQ ID NO). The SEQ ID NOs correspond numerically to the sequence identifiers <400>1 (SEQ ID NO:1), <400>2 (SEQ ID NO:2), etc. A summary of the sequence identifiers is provided in Table 1. A sequence listing is provided after the claims.

The present disclosure teaches artificially modified Class II solanaceous defensins which constitute a new family of defensins with anti-pathogen activity. In an embodiment, anti-pathogen activity is enhanced in the modified Class II solanaceous defensins with respect to inter alia one or more of level and/or spectrum of activity, stability and/or membrane permeabilization capacity compared to the Class II solanaceous defensin prior to modification. The modified defensins are taught herein to be useful in horticulture and agriculture to control pathogen infestation and growth as well as in the manufacture of animal and human medicaments. They may be used alone or in combination with a chemical pathogenicide, an anti-pathogen protein and/or a proteinase inhibitor or precursor form thereof. The availability of the new family of defensins also assists in combating against pathogen resistance to a particular defensin.

A Class II solanaceous defensin is used as a backbone wherein the loop region between the first β-strand (β-strand 1) and the α-helix on the defensin N-terminal end portion (also described as the first flexible loop) is modified by an amino acid substitution, addition and/or deletion and/or a loop region from another defensin, or a modified form thereof, is grafted onto the Class II solanaceous defensin to replace all or part of this loop region. The backbone defensin may also optionally comprise additional mutations outside this loop region. When present, from 1 to about 50 additional mutations in the form of an amino acid substitution, addition and/or deletion may be made to one or more regions outside the Loop 1B region.

An artificially created defensin is provided comprising:

(i) an amino acid backbone derived from or corresponding to a Class II solanaceous defensin having a loop domain within its N-terminal end region;

(ii) the loop domain on the backbone being subjected to one or more of: (a) an amino acid substitution, addition and/or deletion; and/or (b) replacement of all or part of the first loop domain by a loop or a modified form thereof from another defensin;

wherein the artificially created defensin exhibits anti-pathogen activity. The disclosure teaches a single or multiple amino acid substitution, addition and/or deletion which includes converting a Class II solanaceous defensin first loop domain and in particular Loop 1B, to an amino acid sequence corresponding to the loop domain of a Class I defensin. Alternatively, another Class II defensin Loop 1B region is used to replace a Loop 1B on a Class II defensin. The modified Class II solanaceous defensin may also contain one or more additional amino acid substitutions, additions and/or deletions outside this loop region. If present, from 1 to about 50 additional mutations may be located outside the loop region.

In an embodiment, the anti-pathogen activity is enhanced compared to the Class II defensin prior to modification. By “enhanced” means an improvement in one or more of level and/or spectrum of activity, stability and/or membrane permeabilization capacity compared to the non-modified Class II defensin.

Class II solanaceous defensins for use as a backbone include a defensin having at least 70% amino acid sequence similarity over an approximately 20 contiguous amino acid residue sequence at the C-terminal end of the NaD1 mature domain including the most C-terminal invariant cysteine (C) residue (SEQ ID NO:52). Examples of Class II solanaceous defensins include NaD1, NsD1, NsD2, PhD1, PhD2, TPP3, FST, NeThio1, NeThio2, NpThio1, Na-gth and Cc-gth. Other backbone defensins include C20 from Capsicum and SL549 from Nicotiana. NsD1 and NsD2 are from Nicotiana suaveolens, with amino acid sequences as set forth in SEQ ID NOs:49 and 51, respectively.

Reference to the “loop domain” at the N-terminal end region of the Class II solanaceous defensin includes the entire loop region defined by being flanked by the first two (invariant) cysteine (C) amino acid residues. This is the first flexible loop in the defensin in its N-terminal region. However, in an embodiment, the “loop domain” refers to the loop region beginning at the end of the first β-strand and ending at the N-terminal side of the second invariant cysteine amino acid residue. This region is referred to as “L1B” [Loop 1B] in FIG. 5. In NaD1, an example of a Class II solanaceous defensin, this region or domain comprises the amino acid sequence, in single letter code, NTFPGI (see FIG. 5). Other Class II solanaceous defensin first loop regions are shown in FIG. 3. FIG. 4 is a representation of amino acid sequence alignments of different classes of defensins showing the eight conserved cysteine residues.

Hence, the Loop 1B region of the Class II solanaceous defensin backbone may be mutated or a Loop 1B region from another defensin such as from a Class I defensin or another Class II defensin may be grafted in its place to generate a Loop 1B amino acid sequence of X₁ X₂ X₃ X₄ X₅ X₆, (SEQ ID NO:1) wherein:

X₁ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof;

X₂ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof;

X₃ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof;

X₄ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof;

X₅ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof; and/or

X₆ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof;

using single letter amino acid nomenclature, wherein the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆ in the mutated Class II solanaceous defensin does not correspond to an amino acid sequence of the Loop 1B region from the Class II solanaceous defensin forming the backbone prior to modification.

In an embodiment, the Loop 1B region of the Class II solanaceous defensin backbone is mutated or a Loop 1B region from another defensin such as from a Class I defensin is grafted in its place to generate an amino acid sequence of X₁ X₂ X₃ X₄ X₅ X₆ (SEQ ID NO:86) wherein:

X₁ is N, G, D, H, K, A, E, Q, T, P, L, M, S, or R;

X₂ is K, R, G, H, L, N, F, I, S, T or Y;

X₃ is W, Y, H, L, G, F or P;

X₄ is P, K, S, R, H, T, E, V, N, Q, D or G;

X₅ is S, K, Y, F, G or H; and/or

X₆ is P, V, L, T, A, F, N, K, R, M, G, H, I or Y;

using single letter amino acid nomenclature, wherein the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆ does not correspond to an amino acid sequence of the Loop 1B region from the Class II solanaceous defensin forming the backbone prior to modification.

In another embodiment, the Loop 1B region of the Class II solanaceous defensin backbone is mutated or a Loop 1B region from another defensin such as from a Class I defensin is grafted in its place to generate an amino acid sequence of X₁ X₂ X₃ X₄ X₅ X₆, (SEQ ID NO:55) wherein:

X₁ is N, H, Q, D, K or E;

X₂ is R, H, T, K or G;

X₃ is F, H, Y or W;

X₄ is P, K, S or R;

X₅ is G or F; and/or

X₆ is P, V, I, N;

using single letter amino acid nomenclature, wherein the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆ does not correspond to an amino acid sequence of the Loop 1B region from the Class II solanaceous defensin prior to modification.

In an embodiment, the artificially created or modified defensin comprises the amino acid sequence as set forth in SEQ ID NO:57. In this sequence, the Loop 1B region is defined as X₁ X₂ X₃ X₄ X₅ X₆ (SEQ ID NO:56) wherein:

X₁ is an amino acid selected from the list consisting of: L, F, S, I, A, H, Y, Q, D, K, G;

X₂ is an amino acid selected from the list consisting of: S, V, F, I, K, L, A, P, N, T, R, H, G;

X₃ is an amino acid selected from the list consisting of: A, F, W, N, I, S, Y, P, L, H;

X₄ is an amino acid selected from the list consisting of: K, G, E, R, A, P, F, Q, V, S;

X₅ is an amino acid selected from the list consisting of: M, G, K, D, S, Y, P, E, N, F; and

X₆ is an amino acid selected from the list consisting of: V, T, M, S, W, A, P, G, E, K, L, H, I, N.

In an embodiment, the artificially created or modified defensin comprises the amino acid sequence as set forth in SEQ ID NO:84. In this sequence, the Loop 1B region is defined as X₁ X₂ X₃ X₄ X₅ X₆ (amino acids 8-13 of SEQ ID NO:84) wherein: X₁ is an amino acid selected from the list consisting of: N, H, Q, D, K, E;

X₂ is an amino acid selected from the list consisting of: R, H, T, K, G;

X₃ is an amino acid selected from the list consisting of: F, H, Y W;

X₄ is an amino acid selected from the list consisting of: P, K, S, R;

X₅ is an amino acid selected from the list consisting of: G, F; and

X₆ is an amino acid selected from the list consisting of: P, V, I, N.

In an embodiment, taught herein is an isolated solanaceous Class II defensin having anti-pathogen activity comprising an amino acid sequence as set forth in SEQ ID NO:39 or an amino acid sequence having at least 70% similarity to SEQ ID NO:39, the modification being an amino acid substitution, addition or deletion to a Loop 1B amino acid sequence in the Class II solanaceous defensin. SEQ ID NO:39 is the amino acid sequence of the NaD2 Loop 1B sequence (HRFKGP) in an NaD1 backbone to create HXP4. The present disclosure does not extend to NaD1 but to a modified NaD1 in which its Loop 1B sequence has been altered. The present disclosure further does not extend to FST, NeThio1, NeThio2, C20, SL549, PhD1, PhD2, TPP3, Na-gth or Cc-gth but to a modified form of FST, NeThio1, NeThio2, C20, SL549, PhD1, PhD2, TPP3, Na-gth or Cc-gth in which its Loop 1B sequence has been altered.

As indicated above, these aspects apply to any Class II solanaceous defensin including a defensin having an amino acid sequence similarity of 70% or more to the approximately 20 contiguous amino acid residue sequence at the C-terminal end region of the NaD1 mature domain. The 20 contiguous amino acid sequence is defined by SEQ ID NO:52.

In an embodiment, the Loop 1B region on the backbone amino acid sequence is modified to HRFKGP (SEQ ID NO:29), QHHSFP (SEQ ID NO:30), DTYRGV (SEQ ID NO:31), or to any one of SEQ ID NOs:67 to 79, PTWEGI (SEQ ID NO:32), DKYRGP (SEQ ID NO:33), KTFKGI (SEQ ID NO:34), KTWSGN (SEQ ID NO:35), EGWGK (SEQ ID NO:91), GTWSGV (SEQ ID NO:37) or AGFKGP (SEQ ID NO:38) [using single letter amino acid nomenclature]. Conveniently, this is accomplished by grafting the Loop 1B region from NaD2 (SEQ ID NO:29)(HRFKGP), γ-zeathionin2 (SEQ ID NO:30)(QHHSFP), PsD1 (SEQ ID NO:31)(DTYRGV), MsDef1 (SEQ ID NO:33)(DKYRGP), SoD2 (SEQ ID NO:34)(KTFKGI) or DmAMP1 (SEQ ID NO:35)(KTWSGN) or a Loop 1B defined by SEQ ID NOs:67 to 79 onto the Class II solanaceous defensin backbone at the site of its Loop 1B amino acid sequence or modifying an existing Loop 1B region to generate a Loop 1B amino acid sequence selected from HRFKGP (SEQ ID NO:29), QHHSFP (SEQ ID NO:30), DTYRGV (SEQ ID NO:31), DKYRGP (SEQ ID NO:33), KTFKGI (SEQ ID NO:34) and KTWSGN (SEQ ID NO:35). The Class II solanaceous defensin may comprise the modified loop region alone or in combination with an amino acid substitution, addition and/or deletion to the defensin backbone outside the loop region. As indicated above, a Loop 1B as defined in SEQ ID NOs:67 to 79 may also be used or a Class II solanaceous Loop 1B may be substituted onto another Class II solanaceous defensin backbone.

An artificially created defensin is therefore provided comprising a backbone amino acid sequence from a Class II solanaceous defensin having a loop region between the first β-strand and the α-helix on the N-terminal end portion of the defensin wherein the loop region is modified by an amino acid substitution, deletion and/or addition to generate a defensin which has anti-pathogen activity.

In an embodiment, there is provided an artificially created defensin comprising a backbone amino acid sequence from a Class II solanaceous defensin having a Loop 1B region N-terminal to the second invariant cysteine residue wherein the Loop 1B region is modified by an amino acid substitution, addition and/or deletion to generate a defensin which has anti-pathogen activity.

Another embodiment provides an artificially created defensin comprising a backbone amino acid sequence from a Class II solanaceous defensin having a Loop 1B region N-terminal to the second invariant cysteine residue wherein the Loop 1B region is modified by an amino acid substitution, addition and/or deletion to generate a defensin which has enhanced anti-pathogen activity compared to the Class II solanaceous defensin prior to modification, wherein the Class II solanaceous defensin comprises a C-terminal portion of the mature domain having at least about 70% similarity to the amino acid sequence set forth in SEQ ID NO:52 after optimal alignment. Reference to “an amino acid substitution, addition and/or deletion” means one or more substitutions, additions and/or deletions.

In an embodiment, an artificially modified solanaceous Class II defensin having anti-pathogen activity comprising an amino acid sequence as set forth in SEQ ID NO:57 or an amino acid sequence having at least 70% similarity to SEQ ID NO:57 after optimal alignment, the modification being to the solanaceous Class II defensin Loop 1B region.

In an embodiment, an artificially modified solanaceous Class II defensin having anti-pathogen activity comprising an amino acid sequence as set forth in SEQ ID NO:84 or an amino acid sequence having at least 70% similarity to SEQ ID NO:84 after optimal alignment, the modification being to the solanaceous Class II defensin Loop 1B region.

In an embodiment, the anti-pathogen activity is enhanced with respect to inter alia one or more of level and/or spectrum of activity, stability and/or membrane permeabilization compared to the Class II solanaceous defensin, prior to modification. In an embodiment, the anti-pathogen activity is anti-fungal activity. In an embodiment, the anti-pathogen activity is anti-insecticidal activity.

In a further embodiment, an artificially created defensin is provided comprising a backbone amino acid sequence from a Class II solanaceous defensin having a loop region between the first β-strand and the α-helix on the N-terminal end portion of the Class II solanaceous defensin, the defensin selected from the list consisting of NaD1, NsD1, NsD2, PhD1, PhD2, TPP3, FST, NeThio1, NeThio2, NpThio1, Na-gth, Cc-gth, C20 and SL549 and wherein the loop region is modified by an amino acid substitution, addition and/or deletion to generate a loop region comprising the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆, SEQ ID NO:1, wherein each of X₁ through X₆ is an amino acid residue and wherein X₁ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof; X₂ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof; X₃ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof; X₄ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof; X₅ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof; and/or X₆ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof; wherein the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆ does not correspond to an amino acid sequence of a Loop 1B region from a Class II solanaceous defensin; thereby generating a defensin which has anti-pathogen activity. In an embodiment, the loop region is Loop 1B located on the N-terminal side of the second invariant cysteine residue.

In an embodiment, there is provided an artificially created defensin comprising a backbone amino acid sequence from a Class II solanaceous defensin having a loop region between the first β-strand and the α-helix on the N-terminal end portion of the Class II solanaceous defensin, the defensin selected from the list consisting of NaD1, NsD1, NsD2, PhD1, PhD2, TPP3, FST, NeThio1, NeThio2, NpThio1, Na-gth, Cc-gth, C20 and SL549 and wherein the loop region is modified by an amino acid substitution, addition and/or deletion to generate a loop region comprising the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆, SEQ ID NO:86, wherein each of X₁ through X₆ is an amino acid residue wherein X₁ is N, G, D, H, K, A, E, Q, T, P, L, M, S, or R; X₂ is K, R, G, H, L, N, F, I, S, T or Y; X₃ is W, Y, H, L, G, F or P; X₄ is P, K, S, R, H, T, E, V, N, Q, D or G; X₅ is S, K, Y, F, G or H; and X₆ is P, V, L, T, A, F, N, K, R, M, G, H, T or Y wherein the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆ does not correspond to an amino acid sequence of a Loop 1B region from a Class II solanaceous defensin; thereby generating a defensin which has anti-pathogen activity. In an embodiment, the loop region is Loop 1B located on the N-terminal of the second invariant cysteine residue.

In an embodiment, an artificially created defensin is provided comprising a backbone amino acid sequence from a Class II solanaceous defensin having a loop region between the first β-strand and the α-helix on the N-terminal end portion of the Class II solanaceous defensin, the defensin selected from the list consisting of NaD1, NsD1, NsD2, PhD1, PhD2, TPP3, FST, NeThio1, NeThio2, NpThio1, Na-gth, Cc-gth, C20 and SL549 wherein the loop region on the defensin backbone is replaced with a loop region from a defensin selected from the list consisting of NaD2 (SEQ ID NO:29)(HRFKGP), Zea2 (SEQ ID NO:30)(QHHSFP), PsD1 (SEQ ID NO:31)(DTYRGV), MsDef1 (SEQ ID NO:33) (DKYRGP), SoD2 (SEQ ID NO:34) (KTFKGI) and DmAMP1 (SEQ ID NO:35)(KTWSGN) or a modified form thereof or a Loop 1B sequence selected from SEQ ID NO:67 to 79, to generate a defensin which has anti-pathogen activity.

In an embodiment, the loop region is modified by 1 or 2 or 3 or 4 or 5 or 6 amino acid substitutions, additions and/or deletions. In an embodiment, the Class II solanaceous defensin comprises both a modified loop region and an amino acid substitution, addition and/or deletion in a region of the backbone outside the loop region. When present, from 1 to about 50 amino acid substitutions, additions and/or deletions may be made to outside the loop region.

The pathogen may be a fungus (filamentous or non-filamentous), microorganism, insect, arachnid, nematode, protozoa or virus. In an embodiment, the pathogen is a fungus. In another embodiment, the pathogen is an insect. The term “enhanced anti-pathogen activity” includes a broader spectrum of action, higher level of activity, greater stability and/or enhanced membrane permeabilization activity.

In an embodiment, the pathogen is a fungus including a plant fungus and an animal fungus. An “animal fungus” includes a fungus which infects mammals including humans, such as a basidiomycete and an ascomycete.

Compositions comprising the artificially created defensin molecule as well as nucleic acid molecules encoding same are also provided herein. The compositions may be for use in or on plants or in or on animals, such as mammals including humans. The compositions may contain additional agents such as a chemical pathogenicide, proteinaceous pathogenicide and/or a serine or cysteine proteinase inhibitor or a precursor thereof.

Further provided are protocols for generating pathogen-resistant plants as well as treating plants and animals including mammals such as humans to treat or prevent pathogen infestation, growth and/or maintenance. The present disclosure further teaches the use of an artificially created defensin comprising a backbone amino acid sequence from a Class II solanaceous defensin having a loop region between the first β-strand and the α-helix on the N-terminal end portion of the Class II solanaceous defensin wherein the loop region is modified by an amino acid substitution, addition and/or deletion in the manufacture of an anti-pathogen medicament. In as aspect, a chemical or proteinaceous pathogenicide and/or a proteinase inhibitor or precursor thereof is or are used in combination with the modified defensin. In one aspect, a single genetic construct encodes a modified defensin comprising an altered Loop 1B region and a proteinase inhibitor or precursor form thereof such as NaPin1A (from Nicotiana alata), bovine pancreatic trypsin inhibitor (BPTI), tomato cystatin, inhibitor, S1Cys9, or barley cystatin, HvCPI6. In another embodiment, multiple constructs are used each separately encoding one or more of a modified defensin and a proteinase inhibitor or precursor form thereof.

In an embodiment, the loop region is Loop 1B.

In an embodiment, there is provided an isolated defensin from the Australian native, Nicotiana suaveolens, and its use as a backbone defensin molecule. The N. suaveolens defensins include NsD1 and NsD2. The nucleotide sequence of NsD1 and corresponding amino acid sequence are set forth in SEQ ID NOs:48 and 49, respectively. The nucleotide sequence of NsD2 and corresponding amino acid sequence are set forth in SEQ ID NOs:49 and 51, respectively. An N. suaveolens defensin carrying a modified Loop 1B alone or in combination with from 1 to about 50 amino acid substitutions, additions and/or deletions to the backbone is also contemplated herein. An isolated nucleic acid molecule encoding the N. suaveolens defensin is also provided for example, operably linked to a heterologous promoter and/or to a vector nucleic acid molecule.

Accordingly, another aspect taught herein is an isolated defensin from Nicotiana suaveolens having an amino acid sequence as set forth in SEQ ID NO:49 [NsD1] or an amino acid sequence having at least 70% thereto after optimal alignment. Another aspect taught herein is directed to an isolated defensin from Nicotiana suaveolens having an amino acid sequence as set forth in SEQ ID NO:51 [NsD2] or an amino acid sequence having at least 70% thereto after optimal alignment.

According to these aspects, the N. suaveolens defensin may be in isolated, purified form or as part of a formulation or composition comprising the defensin and a diluent, carrier, excipient, preservative, stabilizer and/or a solid or liquid additive.

Isolated nucleic acid molecules encoding NsD1 (SEQ ID NO:48) and NsD2 (SEQ ID NO:50), are provided herein as well as nucleic acid molecules having a nucleotide sequence with at least 70% identity to SEQ ID NO:48 or SEQ ID NO:50 after optimal alignment or a nucleic acid molecule which hybridizes to SEQ ID NO:48 or SEQ ID NO:50 or a complementary form thereof under medium stringent conditions, for example, operably linked to a heterologous promoter and/or to a vector nucleic acid molecule.

When the modified defensin is used in combination with another agent such as a proteinase inhibitor or a cystatin, a single genetic construct encoding all the proteins may be used to transform a plant cell or multiple constructs, each encoding a protein. Alternatively, a plant modified to express a defensin, may be subject to the topical application of a proteinase inhibitor or chemical pathogenicide.

A summary of sequence identifiers used throughout the subject specification is provided in Table 1.

TABLE 1 Summary of sequence identifiers SEQUENCE ID NO: DESCRIPTION 1 Generic amino acid sequence of Loop 1B region 2 Amino acid sequence of portion of NaD1 (Nicotiana alata) containing Loop 1B 3 Amino acid sequence of portion of PhD1 (Petunia hybrida) containing Loop 1B 4 Amino acid sequence of portion of PhD2 (Petunia hybrida) containing Loop 1B 5 Amino acid sequence of portion of TPP3 (Solanum lycopersicum) containing Loop 1B 6 Amino acid sequence of portion of FST (Nicotiana tabacum) containing Loop 1B 7 Amino acid sequence of portion of g-thionin (Nicotiana excelsior) containing Loop 1B [NeThio1] 8 Amino acid sequence of portion of g-thionin (Nicotiana excelsior) containing Loop 1B [NeThio2] 9 Amino acid sequence of portion of g-thionin (Nicotiana attenuata) containing Loop 1B [Na-gth] 10 Amino acid sequence of portion of g-thionin (Nicotiana paniculata) containing Loop 1B [NpThio1] 11 Amino acid sequence of portion of g-thionin (Capsicum chinense) containing Loop 1B [Cc-gth] 12 Amino acid sequence of Loop 1B from NaD1, NsD1 and NsD2 13 Amino acid sequence of Loop 1B from PhD1 14 Amino acid sequence of Loop 1B from PhD2 15 Amino acid sequence of Loop 1B TPP3 16 Amino acid sequence of Loop 1B FST 17 Amino acid sequence of Loop 1B g-thionin (N. excelsior) [NeThio1] 18 Amino acid sequence of Loop 1B g-thionin (N. excelsior) [NeThio2] 19 Amino acid sequence of Loop 1B g-thionin (N. attenuata) [Na-gth] 20 Amino acid sequence of Loop 1B g-thionin (N. paniculata) [NpThio1] 21 Amino acid sequence of Loop 1B g-thionin (C. chinense) [Cc-gth] 22 Amino acid sequence of defensin NaD2 containing Loop 1B 23 Amino acid sequence of defensin g1-H containing Loop 1B 24 Amino acid sequence of defensin Psd1 containing Loop 1B 25 Amino acid sequence of defensin MsDef1 containing Loop 1B 26 Amino acid sequence of defensin DmAMP1 containing Loop 1B 27 Amino acid sequence of defensin RsAFP2 containing Loop 1B 28 Amino acid sequence of defensin g-zeathionin2 (Zea2) containing Loop 1B 29 Amino acid sequence of Loop 1B from NaD2 30 Amino acid sequence of Loop 1B from Zea2 31 Amino acid sequence of Loop 1B from PsD1 32 Amino acid sequence of Loop 1B from PsD2 33 Amino acid sequence of Loop 1B from MsDef1 34 Amino acid sequence of Loop 1B from SoD2 35 Amino acid sequence of Loop 1B from DmAMP1 36 Amino acid sequence of Loop 1B from VrD1 37 Amino acid sequence of Loop 1B from RsAFP2 38 Amino acid sequence of Loop 1B from g1-H 39 Amino acid sequence of HXP4 (NaD2 Loop 1B [NaD2L1B] in NaD1) 40 Amino acid sequence of HXP34 (Zea2 Loop 1B [Zea2L1B] in NaD1) 41 Amino acid sequence of HXP35 (PsD1 Loop 1B [PsDL1B] in NaD1) 42 Amino acid sequence of HXP91 (MsDeF1 Loop 1B [MsDef1L1B] in NaD1) 43 Amino acid sequence of HXP92 (SoD1 Loop 1B [SoD1L1B] in NaD1) 44 Amino acid sequence of HXP58 (DmAMP1 Loop 1B [DMAMPL1B] in NaD1) 45 Amino acid sequence of HXP37 (VrD1 Loop 1B [VrD1L1B] in NaD1) 46 Amino acid sequence of HXP72 (NaD2 Loop 1B [NaD2L1B] in PhD2) 47 Amino acid sequence of HXP95 (NaD2 Loop 1B [NaD2L1B] in NsD1 48 Nucleotide sequence encoding defensin from Nicotiana suaveolens 49 Amino acid sequence of NsD1 50 Nucleotide sequence encoding NsD2 from Nicotiana suaveolens 51 Amino acid sequence encoding NsD2 52 Amino acid sequence of C-terminal end amino acid sequence of NaD1 which ends and includes the most C-terminal invariant cysteine residue 53 Amino acid sequence of NaD1 C-terminal tail 54 Amino acid sequence of variable region of Loop 1B region 55 Amino acid sequence of variable region of Loop 1B region 56 Amino acid sequence of variable region of Loop 1B region 57 Amino acid sequence of NaD1 backbone having a Loop 1B defined by X₁ through X₆ 58 Amino acid sequence of C20 59 Amino acid sequence of SL549 60 Amino acid sequence of Loop 1B from C20 61 Amino acid sequence of NaPin1A 62 Amino acid sequence of BPTI 63 Amino acid sequence of CI-1B 64 Amino acid sequence of HVCPI6 65 Amino acid sequence of S1Cys9 66 Amino acid sequence of OsIa 67 Amino acid sequence at replacement Loop 1B identified following high through put screen 68 Amino acid sequence at replacement Loop 1B identified following high through put screen 69 Amino acid sequence at replacement Loop 1B identified following high through put screen 70 Amino acid sequence at replacement Loop 1B identified following high through put screen 71 Amino acid sequence at replacement Loop 1B identified following high through put screen 72 Amino acid sequence at replacement Loop 1B identified following high through put screen 73 Amino acid sequence at replacement Loop 1B identified following high through put screen 74 Amino acid sequence at replacement Loop 1B identified following high through put screen 75 Amino acid sequence at replacement Loop 1B identified following high through put screen 76 Amino acid sequence at replacement Loop 1B identified following high through put screen 77 Amino acid sequence at replacement Loop 1B identified following high through put screen 78 Amino acid sequence at replacement Loop 1B identified following high through put screen 79 Amino acid sequence at replacement Loop 1B identified following high through put screen 80 Nucleotide sequence of construct expressing HvCPI6 for expression in corn 81 Amino acid sequence of HvCPI6 82 Nucleotide sequence of construct comprising HvCPI6-L-HXP4-CTPP (NaD1) 83 Amino acid sequence of HvCPI6-L-HXP4-CTPP (NaD1) 84 Amino acid sequence of NaD1 backbone having a Loop 1B defined by X₁ through X₆ 85 Amino acid sequence of TPP3 backbone having a Loop 1B from NaD2 (HXP107)

Table 2 provides a summary of the nomenclature used to describe the exemplified modified defensin.

TABLE 2 Summary of nomenclature of modified defensins Nomenclature Description HXP4 NaD2 Loop 1B in NaD1 backbone HXP34 Zea2 Loop 1B in NaD1 backbone HXP35 PSD1 Loop 1B in NaD1 backbone HXP37 VrD1 Loop 1B in NaD1 backbone HXP91 MsDeF1 Loop 1B in NaD1 backbone HXP92 SoD2 Loop 1B in NaD1 backbone HXP58 DmAMP1 Loop 1B in NaD1 backbone HXP72 NaD2 Loop 1B in PhD2 backbone HXP95 NaD2 Loop 1B in NsD1 backbone HXP107 NaD2 Loop 1B in TPP3 backbone

Table 3 is a list of single and three letter code for amino acid residues used herein.

TABLE 3 List of single and three letter abbreviations for amino acid residues Amino Acid Three-letter Abbreviation One-letter Symbol Alanine Ala A Arginine Arg R Asparagine Asn N Aspartic acid Asp D Cysteine Cys C Glutamine Gln Q Glutamic acid Glu E Glycine Gly G Histidine His H Isoleucine Ile I Leucine Leu L Lysine Lys K Methionine Met M Phenylalanine Phe F Proline Pro P Serine Ser S Threonine Thr T Tryptophan Trp W Tyrosine Tyr Y Valine Val V

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a schematic representation of the defensins, NaD1, RsAFP1, VrD2 and Brazzein showing common disulfide bonding pattern and common structural fold in which a triple-stranded, anti-parallel β-sheet is tethered to an α-helix by three disulfide bonds, forming a cysteine-stabilized αβ motif (CSαβ). A fourth disulfide bond also joins the N- and C-termini leading to a stable structure.

FIG. 2 is a diagrammatic representation showing breakdown of defensins into 16 groups based on sequence similarity.

 Antifungal

 Pollen recognition ▴ Protein synthesis inhibitor

 Sweet tasting ▪ Antibacterial

 Zinc tolerance

 α-amylase inhibitor

 Trypsin inhibitor

 Sodium channel blocker

FIGS. 3A and B are representations of sequence alignments of the Class II solanaceous defensins NaD1, NsD1, NsD2, PhD1, PhD2, TPP3, FST, NeThio1, NeThio2, Na-gth, NpThio1 and Cc-gth. The amino acid sequences are given in the Sequence Listing as follows: NaD1, SEQ ID NO:2; NsD1, SEQ ID NO:49; NsD2, SEQ ID NO:51; PhD1, SEQ ID NO:3; PhD2, SEQ ID NO:4; TPP3, SEQ ID NO:5; FST, SEQ ID NO:6; NeThio1, SEQ ID NO:7; NeThio2, SEQ ID NO:8; Na-gth, SEQ ID NO:9; NpThio1, SEQ ID NO:10; and Cc-gth, SEQ ID NO:11. The shading in FIG. 3A depicts the high level of conservation between the sequences.

FIG. 4 is a representation of sequence alignment of defensins of different classes which reveals, apart from the eight cysteine residues which are conserved, only the amino acids at positions 7 and 10 are highly conserved. Numbering is based relative to NaD1. The sequences are given in the Sequence Listing as follows: NaD1, SEQ ID NO:2; PhD2, SEQ ID NO:4; NaD2, SEQ ID NO:22; g1-H, SEQ ID NO 23; Psd1, SEQ ID NO 24; Ms-Def1, SEQ ID NO 25; Dm-AMP1, SEQ ID NO 26; Rs-AFP2, SEQ ID NO 27; and g-zeathionin2, SEQ ID NO 28.

FIG. 5 is a diagrammatic representation of the loop structure of NaD1 showing the location of Loop 1B connecting β-strand 1 and the α-helix. The amino acid sequence is also given in SEQ ID NO:2.

FIG. 6A is a representative of an immunoblot depicting expression and purification of recombinant NaD1 (rNaD1). P. pastoris expression medium collected at 48 hours (30 μL) as well as samples from various stages of SP sepharose purification including the unbound fraction (30 μL), wash fraction (30 μL) and the first five 1.5 mL elution fractions (30 μL of each) were separated by SDS-PAGE and examined by immunoblotting with the α-NaD1 antibody. NaD1 from flowers (200 ng) was used as a positive control. rNaD1 could be detected in the 48 hour expression media as well as the SP sepharose elution fractions.

FIG. 6B is a representation of a reverse phase HPLC trace illustrating purity of rNaD1 purified from P. pastoris using SP sepharose. SP sepharose elution fractions containing rNaD1 were loaded onto an analytical C8 RP-HPLC column and eluted using a 40 min linear gradient (0-100% buffer B). Proteins were detected by absorbance at 215 nm. A single major protein was detected indicating the protein was highly pure.

FIG. 6C is a representation of the structure of rNaD1 to native NaD1 purified from flowers. The far UV circular dichroism spectra of rNaD1 (Open squares) and native NaD1 (closed diamonds) was compared and demonstrated no significant differences indicating that rNaD1 was correctly folded.

FIG. 6D is a representation of the anti-fungal activity of rNaD1 to native NaD1 purified from flowers. Hyphal growth of Fusarium oxysporum f. sp. vasinfectum in the presence of rNaD1 (open squares) or native NaD1 (closed diamonds) is plotted relative to the growth of a no protein control for the same period. Graph represents data from three separate experiments performed in quadruplicate. Error bars represent standard error of the mean.

FIG. 7 is a graphical representation of the anti-fungal activity against Fusarium graminearum of Class I defensins used for the loop swaps compared to NaD1 and NsD1.

FIG. 8 is a graphical representation of the relative anti-fungal activity of loop variants HXP4, HXP34 and HXP35 compared to NaD1 against F. graminearum (Fgr).

FIG. 9 is a graphical representation of the relative anti-fungal activity of loop variants HXP4, HXP34 and HXP35 compared to NaD1 against F. verticilloides (Fve).

FIG. 10 is a graphical representation of the relative anti-fungal activity of loop variants HXP4, HXP34 and HXP35 compared to NaD1 against C. graminicola (Cgr).

FIG. 11 is a diagrammatic representation of pHEX138 construct. The DNA was inserted between the left and right borders of the binary vector pBIN19 (Bevan (1984) Nucleic Acids Research 12:8711-8721). The DNA was produced by modifying the NaD1 gene.

Abbreviations in clockwise order are: oriV: origin of vegetative replication ColE1 orl: replication origin derived from colicin E1; TDNA RB: right border of Agrobacterium tumefaciens TDNA; Nos promoter: promoter of nopaline synthase Nos gene; NPTII: genetic sequence encoding neomycin phosphotransferase II; Nos terminator: terminator sequence of Nos gene; Disrupted lacZ: DNA segment encoding partial sequence of B-galactosidase; CaMV 35S promoter: promoter of Cauliflower mosaic virus (CaMV) 35S protein; HXP4: DNA encoding NaD2 Loop 1B [NaD2L1B] in NaD1 plus the CTPP; CaMV 35S terminator: terminator sequence of genes encoding CaMV 35S protein; M13 on: origin of M13 virus replication; TDNA LB: TDNA left border; All arrows indicate direction of transcription.

FIG. 12 is a graphical representation of the relative anti-fungal activity of the loop variant HXP4 compared to NaD1 against Aspergillus niger.

FIGS. 13A through C are graphical representations of the relative anti-fungal activity of HXP4 compared to NaD1 against Cryptococcus spp.

FIG. 14A through C are graphical representations of the effects of HXP4 on germination (24 hours, A), appresorium (24 hours, B) and post-appresorium structure (48 hours, C) on Asian soybean rust (Phakopsora pachyrhizi) compared to NaD1.

FIG. 15 is a representation of the nucleotide sequences (SEQ ID NO:80) of a construct comprising a nucleotide sequence encoding HvCPI6 (a barley cystatin) for use in corn. The amino acid sequence of HvCPI6 (SEQ ID NO:81) is also provided.

FIG. 16 is a representation of the nucleotide sequence (SEQ ID NO:82) of a construct comprising a nucleotide sequence encoding HvCPI6 (a barley cystatin) and the modified defensin HXP4 for use in corn. The amino acid sequence of HvCPI6 and HXP4 (SEQ ID NO:83) is also given.

DETAILED DESCRIPTION

A modified defensin molecule is provided with anti-pathogen activity. The terms “modified defensin”, “variant defensin”, “mutated defensin” and “chimeric defensin” may all be used to describe the modified class II solanaceous defensins herein described. In an embodiment, a Class II solanaceous defensin is modified at the loop region between the first β-strand (β-strand 1) and the α-helix at the N-terminal end portion of the defensin. In an embodiment, the loop region comprises the 6 amino acids N-terminal of the second invariant cysteine residue or its equivalent. This region is defined as “Loop 1B” (see FIG. 5). A Class II solanaceous defensin is distinguished from other defensins by a relatively conserved C-terminal end portion of the mature domain. Reference to a “Class II solanaceous defensin” includes any defensin having at least 70% amino acid sequence similarity to the C-terminal end portion of the NaD1 mature domain, the C-terminal portion of NaD1 comprising approximately 20 contiguous amino acid residues ending and including the most C-terminal invariant cysteine in the NaD1 mature domain (for example, SEQ ID NO:52). By “at least 70%” means at least 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99 or 100%. Table 4 provides the percentage identities between the C-terminal amino acid sequence of NaD1 and a number of Class II solanaceous defensins mature domains.

The Loop 1B amino acid sequence in a Class II solanaceous defensin is modified to the sequence X₁ X₂ X₃ X₄ X₅ X₆ (SEQ ID NO:1) wherein:

X₁ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof;

X₂ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof;

X₃ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof;

X₄ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof;

X₅ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof; and/or

X₆ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V;

using single letter amino acid nomenclature, wherein the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆ does not correspond to an amino acid sequence of the Loop 1B region from the Class II solanaceous defensin prior to modification.

In an embodiment, the Loop 1B sequence in a Class II solanaceous defensin is modified to the sequence X₁ X₂ X₃ X₄ X₅ X₆ (SEQ ID NO:86) wherein:

X₁ is N, G, D, H, K, A, E, Q, T, P, L, M, S, or R;

X₂ is K, R, G, H, L, N, F, I, S, T or Y;

X₃ is W, Y, H, L, G, F or P;

X₄ is P, K, S, R, H, T, E, V, N, Q, D or G;

X₅ is S, K, Y, F, G or H; and/or

X₆ is P, V, L, T, A, F, N, K, R, M, G, H, I or Y;

wherein the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆ does not correspond to an amino acid sequence of the Loop 1B region from the Class II solanaceous defensin prior to modification.

In an embodiment, the Loop 1B sequence in a Class II solanaceous defensin is modified to the sequence X₁ X₂ X₃ X₄ X₅ X₆ (SEQ ID NO:55) wherein:

X₁ is N, H, Q, D, K or E;

X₂ is R, H, T, K or G;

X₃ is F, H, Y or W;

X₄ is P, K, S or R;

X₅ is G or F; and

X₆ is P, V, I or N;

wherein the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆ does not correspond to an amino acid sequence of the Loop 1B region from the Class II solanaceous defensin prior to modification.

Reference to “X₁ X₂ X₃ X₄ X₅ X₆” means 6 contiguous amino acid residues corresponding to a Loop 1B region.

In an embodiment, the artificially created or modified defensin comprises the amino acid sequence as set forth in SEQ ID NO:57. In this sequence, the Loop 1B region is defined as X₁ X₂ X₃ X₄ X₅ X₆ wherein:

X₁ is an amino acid selected from the list consisting of: L, F, S, I, A, H, Y, Q, D, K, G;

X₂ is an amino acid selected from the list consisting of: S, V, F, I, K, L, A, P, N, T, R, H, G;

X₃ is an amino acid selected from the list consisting of: A, F, W, N, I, S, Y, P, L, H;

X₄ is an amino acid selected from the list consisting of: K, G, E, R, A, P, F, Q, V, S;

X₅ is an amino acid selected from the list consisting of: M, G, K, D, S, Y, P, E, N, F; and

X₆ is an amino acid selected from the list consisting of: V, T, M, S, W, A, P, G, E, K, L, H, I, N.

In an embodiment, the artificially created or modified defensin comprises the amino acid sequence as set forth in SEQ ID NO:84. In this sequence, the Loop 1B region is defined as X₁ X₂ X₃ X₄ X₅ X₆ wherein:

X₁ is an amino acid selected from the list consisting of: N, H, Q, d, K, E;

X₂ is an amino acid selected from the list consisting of: R, H, T, K, G;

X₃ is an amino acid selected from the list consisting of: F, H, Y W;

X₄ is an amino acid selected from the list consisting of: P, K, S, R;

X₅ is an amino acid selected from the list consisting of: G, F; and

X₆ is an amino acid selected from the list consisting of: P, V, I, N.

In the case of NaD1, a Class II solanaceous defensin, the Loop 1B amino acid sequence is NTFPGI (SEQ ID NO:12). Consequently, the NTFPGI is modified such that N is replaced by one of X₁ is A, R, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof; the T is replaced by X₂ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, W, Y or V or a naturally occurring modified form thereof; the F is replaced by X₃ is A, R, N, D, C, Q, E, G, H, I, L, K, M, P, S, T, W, Y or V or a naturally occurring modified form thereof; the P is replaced by X₄ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, S, T, W, Y or V or a naturally occurring modified form thereof; the G is replaced by X₅ is A, R, N, D, C, Q, E, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof; and/or the I is replaced by X₆ is A, R, N, D, C, Q, E, G, H, L, K, M, F, P, S, T, W, Y or V; with the proviso that the Loop 1B amino acid sequence does not correspond to the Loop 1B from NaD1. In an embodiment, the Loop 1B region is defined as X₁ X₂ X₃ X₄ X₅ X₆ (SEQ ID NO:56) wherein X₁ is an amino acid selected from the list consisting of: L, F, S, I, A, H, Y, Q, D, K, G; X₂ is an amino acid selected from the list consisting of: S, V, F, I, K, L, A, P, N, T, R, H, G; X₃ is an amino acid selected from the list consisting of: A, F, W, N, I, S, Y, P, L, H; X₄ is an amino acid selected from the list consisting of: K, G, E, R, A, P, F, Q, V, S; X₅ is an amino acid selected from the list consisting of: M, G, K, D, S, Y, P, E, N, F; and X₆ is an amino acid selected from the list consisting of: V, T, M, S, W, A, P, G, E, K, L, H, I, N. The Loop 1B sequence may have a single amino acid change or 2 or 3 or 4 or 5 or all 6 amino acids may be altered. This is encompassed by the expression “single or multiple amino acid substitutions, additions and/or deletions”.

The Class II solanaceous defensin may be modified by any number of amino acid changes to the Loop 1B region alone or in combination with other mutations. Other mutations include amino acid substitutions, additions and/or deletions. Mutations outside the Loop 1B region may number from 1 to about 50. A “change” includes a graft of a Loop 1B region from one defensin onto a Class II solanaceous defensin Loop 1B region. The source may be a Class I defensin Loop 1B or a Loop 1B from another Class II defensin. These aspects are based on the proviso that anti-pathogen activity of the modified defensin against at least one plant or animal pathogen is maintained. In an embodiment, the anti-pathogen activity is enhanced relative to the Class II defensin prior to modification in terms of level or spectrum of activity, stability and/or permeabilization.

Provided herein is an artificially created defensin comprising a modified Class II solanaceous defensin backbone wherein the loop region between β-strand 1 and the α-helix on the N-terminal end portion is modified by a single or multiple amino acid substitution, addition and/or deletion to generate a variant defensin which has anti-pathogen activity. In an embodiment, the loop region is Loop 1B defined by the 6 amino acid residues N-terminal to the second invariant cysteine residue. Reference may be made to FIGS. 3 to 5. Its equivalent region in any defensin is contemplated herein. From 1 to about 6 amino acid changes may be made to the Loop 1B region. In an embodiment, the anti-pathogen activity is anti-fungal or anti-insect activity. In an embodiment, anti-pathogen activity is enhanced in the modified Class II solanaceous defensins with respect to inter alia one or more of level and/or spectrum of activity, stability and/or membrane permeabilization capacity compared to Class II solanaceous defensin prior to modification.

Another aspect taught herein provides an artificially created defensin comprising a backbone amino acid sequence from a Class II solanaceous defensin having a Loop 1B region N-terminal to the second invariant cysteine residue wherein the Loop 1B region is modified by an amino acid substitution, addition and/or deletion to generate a defensin which has anti-pathogen activity.

A “single or multiple amino acid substitution, addition and/or deletion” is encompassed by the expression “an amino acid substitution, addition and/or deletion”. The artificially created defensin represents a new family of defensins. It is taught herein that the modified defensins be used in horticulture and/or agriculture to control pathogen infestation and growth and as medicaments for use in animals or humans. The modified defensins may be used alone or in combination with a chemical pathogenicide, a proteinaceous anti-pathogen agent and/or a serine or cysteine proteinase inhibitor or a precursor form thereof. The ability to select from a panel of defensins helps combat the development of pathogen resistance to a defensin.

When used in combination with a proteinase inhibitor or anti-pathogen agent, these may be separately topically applied or one expressed in a genetically modified plant and another topically applied or all of the modified defensin and proteinase inhibitor and/or anti-pathogen agent expressed on a single or multiple genetic constructs.

By “Loop 1B” is meant the 6 amino acid residues N-terminal of the second invariant cysteine residue or its equivalent as depicted in FIG. 5. Some defensins such as VrD1 and NeThio1 only have five amino acid residues. However, in that case, the Loop 1B region comprises the five residues. It is also be described as the first flexible loop region between β-strand 1 and the α-helix. Loop 1A (see FIG. 5) is the β-strand.

As indicated above, reference to “an amino acid substitution, addition and/or deletion” includes a single or multiple amino acid substitution, addition and/or deletion which encompasses a replacement of a Loop 1B with a Loop 1B from another defensin. Such a replacement is referred to herein as a domain swap, loop swap, grafting or other similar expression. Reference to “another defensin” includes any defensin whether a Class I or Class II defensin (see also FIG. 2). The Class II defensin backbone is optionally further modified by modified by removal of a C-terminal tail (i.e. the CTPP) or by swapping an existing CTPP with another tail and/or the backbone may have a single or multiple amino acid substitution, addition and/or deletion at a location on the backbone outside the loop region referred to above. A “Class II solanaceous defensin” includes any defensin having at least 70% similarity to SEQ ID NO:52 after optimal alignment. SEQ ID NO:52 represents the 20 contiguous amino acid residues ending at and including the most C-terminal cysteine residue in the NaD1 mature domain. Examples of such Class II solanaceous defensins having at least 70% similarity to SEQ ID NO:52 are listed in Table 4.

Hence, taught herein is a modified defensin comprising a Class II solanaceous defensin back bone having an amino acid substitution, addition and/or deletion to its Loop 1B region to generate a modified defensin which has anti-pathogen activity. In an embodiment, the anti-pathogen activity is enhanced relative to the Class II defensin prior to modification.

In an embodiment, a modified defensin is provided comprising a Class II solanaceous defensin back bone having an amino acid substitution, addition and/or deletion to its Loop 1B region to generate a modified defensin which has anti-pathogen activity, the Class II solanaceous defensin comprising an amino acid sequence at its C-terminal end region of its mature domain having at least 70% similarity to SEQ ID NO:52 after optimal alignment.

In an embodiment, an isolated solanaceous Class II defensin having anti-pathogen activity is taught herein comprising an amino acid sequence as set forth in SEQ ID NO:39 or an amino acid sequence having at least 70% similarity to SEQ ID NO:39, the modification being an amino acid substitution, addition or deletion to a Loop 1B amino acid sequence in the Class II solanaceous defensin. In an embodiment, the anti-pathogen activity is anti-fungal activity.

Also taught herein is an artificially modified solanaceous Class II defensin having anti-pathogen activity comprising an amino acid sequence as set forth in SEQ ID NO:57 or an amino acid sequence having at least 70% similarity to SEQ ID NO:57 after optimal alignment, the modification being to the solanaceous Class II defensin Loop 1B region.

In an embodiment, taught herein is an artificially modified solanaceous Class II defensin having anti-pathogen activity comprising an amino acid sequence as set forth in SEQ ID NO:84 or an amino acid sequence having at least 70% similarity to SEQ ID NO:84 after optimal alignment, the modification being to the solanaceous Class II defensin Loop 1B region.

Reference to “at least 70% similarity” includes 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99 and 100% similarity. In an embodiment, this may be referred to as identity.

The present disclosure further provides an artificially created defensin comprising a backbone amino acid sequence from a Class II solanaceous defensin having a loop region between the first β-strand (β-strand 1) and the α-helix on the N-terminal end portion of the Class II solanaceous defensin, the defensin selected from the list consisting of NaD1, NsD1, NsD2, PhD1, PhD2, TPP3, FST, NeThio1, NeThio2, NpThio1, Na-gth, Cc-gth, C20 and SL549 wherein the Loop 1B region is modified by an amino acid substitution, addition and/or deletion to generate a region comprising the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆ (SEQ ID NO:1) each of X₁ through X₆ is an amino acid residue and wherein X₁ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof; X₂ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof; X₃ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof; X₄ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof; X₅ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof; and/or X₆ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof; wherein the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆ does not correspond to an amino acid sequence of the Loop 1B region from the Class II solanaceous defensin prior to modification to thereby generate a defensin which has anti-pathogen activity. In an embodiment, the Loop 1B region is modified by an amino acid substitution, addition and/or deletion to generate a region comprising the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆ (SEQ ID NO:56) each of X₁ through X₆ is an amino acid residue and wherein X₁ is an amino acid selected from the list consisting of: L, F, S, I, A, H, Y, Q, D, K, G; X₂ is an amino acid selected from the list consisting of: S, V, F, I, K, L, A, P, N, T, R, H, G; X₃ is an amino acid selected from the list consisting of: A, F, W, N, I, S, Y, P, L, H; X₄ is an amino acid selected from the list consisting of: K, G, E, R, A, P, F, Q, V, S; X₅ is an amino acid selected from the list consisting of: M, G, K, D, S, Y, P, E, N, F; and X₆ is an amino acid selected from the list consisting of: V, T, M, S, W, A, P, G, E, K, L, H, I, N or a naturally occurring modified form thereof; wherein the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆ does not correspond to an amino acid sequence of the Loop 1B region from the Class II solanaceous defensin prior to modification.

The present disclosure further provides an artificially created defensin comprising a backbone amino acid sequence from a Class II solanaceous defensin having a loop region between the first β-strand (β-strand 1) and the α-helix on the N-terminal end portion of the Class II solanaceous defensin, the defensin selected from the list consisting of NaD1, NsD1, NsD2, PhD1, PhD2, TPP3, FST, NeThio1, NeThio2, NpThio1, Na-gth, Cc-gth, C20 and SL549 wherein the Loop 1B region is modified by an amino acid substitution, addition and/or deletion to generate a region comprising the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆, (SEQ ID NO:86) wherein each of X₁ through X₆ is an amino acid residue and X₁ is N, G, D, H, K, A, E, Q, T, P, L, M, S, or R; X₂ is K, R, G, H, L, N, F, I, S, T or Y; X₃ is W, Y, H, L, G, F or P; X₄ is P, K, S, R, H, T, E, V, N, Q, D or G; X₅ is S, K, Y, F, G or H; and X₆ is P, V, L, T, A, F, N, K, R, M, G, H, I or Y; wherein the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆ does not correspond to an amino acid sequence of the Loop 1B region from the Class II solanaceous defensin prior to modification to thereby generate a defensin which has anti-pathogen activity.

In an embodiment, X₁ is N, H, Q, D, K or E; X₂ is R, H, T, K or G; X₃ is F, H, Y or W; X₄ is P, K, S or R; X₅ is G or F; and/or X₆ is P, V, I or N, wherein the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆ (SEQ ID NO:55) does not correspond to an amino acid sequence of a Loop 1B region from a Class II solanaceous defensin. Examples of Loop 1B sequences from a Class II solanaceous defensin include NTFPGI from NaD1 (N. alata), NsD1 (N. suaveolens), NsD2 (N. suaveolens), NeThio2 (N. excelsior) and FST (N. tabacum); PTWDSV from PhD1 (P. hybrida); PTWEGI from PhD2 (P. hybrida); QTFPGL from TPP3 (S. lycopersicum); NTFEGF from Na-gth (N. attenuata); NTFPGL from Np-Thio 1 (N. paniculata); IFTGL from NeThio1 (N. excelsior) and KHFKGL from Cc-gth (C. chinese). Another Loop 1B sequence is KYFKGL (SEQ ID NO:60).

Still another aspect taught herein relates to an artificially created defensin comprising a backbone amino acid sequence from a Class II solanaceous defensin having a loop region between β-strand 1 and the α-helix on the N-terminal end portion of the Class II solanaceous defensin, the defensin selected from the list consisting of NaD1, NsD1, NsD2, PhD1, PhD2, TPP3, FST, NeThio1, NeThio2, NpThio1, Na-gth and Cc-gth wherein the loop region on the defensin backbone is replaced with a loop region from a defensin selected from the list consisting of NaD2 (HRFKGP), Zea2 (QHHSFP), PSD1 (DTYRGV), MsDef1 (DKYRGP), SoD2 (KTFKGI) and DmAMP1 (KTWSGN) or a modified form thereof, or a Loop 1B sequence selected from SEQ ID NO:67 to 79 to generate a defensin which has anti-pathogen activity.

In an embodiment, the anti-pathogen activity is enhanced compared to the Class II solanaceous defensin prior to modification. Parameters for determining enhanced activity include level and/or spectrum of activity degree of stability and/or level of permeabilization activity. In an embodiment, the loop region is Loop 1B as herein defined. This is the first flexible loop in a defensin.

As indicated above, the Loop 1B region on the Class II solanaceous defensin comprises the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆, each X as hereinbefore defined, wherein at least one or more including in an aspect all 6 (or corresponding 5) amino acid residues is/are replaced, generally but not exclusively, to the sequence corresponding to a Loop 1B or a derivative thereof from another defensin such as a Class I defensin or another Class II defensin.

Also provided is a modified defensin having anti-pathogen activity the modified defensin comprising:

(i) a backbone amino acid sequence derived from a Class II solanaceous defensin, the defensin comprising a Loop 1B region between β-strand 1 and the α-helix on the N-terminal end portion of the defensin;

(ii) the Loop 1B region on the defensin modified by an amino acid substitution, addition, deletion or swap to generate a Loop 1B region analogous or homologous or otherwise functionally similar to another defensin Loop 1B;

(iii) wherein the resulting Loop 1B comprises the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆ (SEQ ID NO:1) wherein:

X₁ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof;

X₂ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof;

X₃ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof;

X₄ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof;

X₅ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V; or a naturally occurring modified form thereof and/or

X₆ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof,

using single letter amino acid nomenclature, wherein the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆ does not correspond to an amino acid sequence of the Loop 1B region from the Class II solanaceous defensin prior to modification.

Also provide is a modified defensin having anti-pathogen activity the modified defensin comprising:

(i) a backbone amino acid sequence derived from a Class II solanaceous defensin, the defensin comprising a Loop 1B region between β-strand 1 and the α-helix on the N-terminal end portion of the defensin;

(ii) the Loop 1B region on the defensin modified by an amino acid substitution, addition, deletion or swap to generate a Loop 1B region analogous or homologous or otherwise functionally similar to another defensin Loop 1B;

(iii) wherein the resulting Loop 1B comprises the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆ (SEQ ID NO:86) wherein:

X₁ is N, G, D, H, K, A, E, Q, T, P, L, M, S, or R;

X₂ is K, R, G, H, L, N, F, I, S, T or Y;

X₃ is W, Y, H, L, G, F or P;

X₄ is P, K, S, R, H, T, E, V, N, Q, D or G;

X₅ is S, K, Y, F, G or H; and/or

X₆ is P, V, L, T, A, F, N, K, R, M, G, H, I or Y,

wherein the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆ does not correspond to an amino acid sequence of the Loop 1B region from the Class II solanaceous defensin prior to modification.

The backbone amino acid sequence may further comprise an amino acid substitution, addition and/or deletion to a region outside the Loop 1B region. If present, from about 1 to about 50 amino acid substitutions, additions and/or deletions may be made to the backbone amino acid sequence outside the Loop 1B region. By “1 to 50” means 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49 or 50. In an embodiment, the additional mutation is in the C-terminal tail (the CTPP) of the Type II solanaceous defensin.

Also provided is a modified defensin comprising a backbone defensin molecule from Nicotiana suaveolens (an Australian native) having a Loop 1B region or its equivalent modified by an amino acid substitution, addition and/or deletion to introduce a Loop 1B sequence comprising X₁ X₂ X₃ X₄ X₅ X₆ (SEQ ID NO:1) wherein:

X₁ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof;

X₂ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof;

X₃ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof;

X₄ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof;

X₅ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof; and/or

X₆ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof,

using single letter amino acid nomenclature, wherein the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆ does not correspond to an amino acid sequence of the Loop 1B region from the Class II solanaceous defensin prior to modification and wherein the modified defensin has anti-pathogen activity. In an embodiment, the N. suaveolens defensin is selected from NsD1 and NsD2.

Another embodiment provided herein comprises a modified defensin comprising a backbone defensin molecule from Nicotiana suaveolens (an Australian native) having a Loop 1B region or its equivalent modified by a single or multiple amino acid substitution, addition and/or deletion to introduce a Loop 1B sequence comprising X₁ X₂ X₃ X₄ X₅ X₆ (SEQ ID NO:86) wherein:

X₁ is N, G, D, H, K, A, E, Q, T, P, L, M, S, or R;

X₂ is K, R, G, H, L, N, F, I, S, T or Y;

X₃ is W, Y, H, L, G, F or P;

X₄ is P, K, S, R, H, T, E, V, N, Q, D or G;

X₅ is S, K, Y, F, G or H; and/or

X₆ is P, V, L, T, A, F, N, K, R, M, G, H, I or Y,

wherein the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆ does not correspond to an amino acid sequence of the Loop 1B region from the Class II solanaceous defensin prior to modification and wherein the modified defensin has anti-pathogen activity. In an embodiment, the N. suaveolens defensin is selected from NsD1 and NsD2.

In an embodiment, X₁ X₂ X₃ X₄ X₅ X₆ (SEQ ID NO:56) comprises an amino acid residue selected from:

X₁ is an amino acid selected from the list consisting of: L, F, S, I, A, H, Y, Q, D, K, G;

X₂ is an amino acid selected from the list consisting of: S, V, F, I, K, L, A, P, N, T, R, H, G;

X₃ is an amino acid selected from the list consisting of: A, F, W, N, I, S, Y, P, L, H;

X₄ is an amino acid selected from the list consisting of: K, G, E, R, A, P, F, Q, V, S;

X₅ is an amino acid selected from the list consisting of: M, G, K, D, S, Y, P, E, N, F; and

X₆ is an amino acid selected from the list consisting of: V, T, M, S, W, A, P, G, E, K, L, H, I, N.

In this regard, the present disclosure further provides an isolated defensin from Nicotiana suaveolens having an amino acid sequence as set forth in SEQ ID NO:49 [NsD1] or an amino acid sequence having at least 70% thereto after optimal alignment. Another aspect of the present disclosure is directed to an isolated defensin from Nicotiana suaveolens having an amino acid sequence as set forth in SEQ ID NO:51 [NsD2] or an amino acid sequence having at least 70% thereto after optimal alignment. Nucleotide sequences encoding NsD1 and NsD2 such as SEQ ID NO:48 or SEQ ID NO:50, respectively, or a nucleotide sequence having at least 70% identity to SEQ ID NO:48 or SEQ ID NO:50 after optimal alignment or which is capable of hybridizing to SEQ ID NO:48 or SEQ ID NO:50 or a complementary form of SEQ ID NO:48 or SEQ ID NO:50 under medium stringency conditions are also contemplated herein. By “at least 70% identity” means at least 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 988, 99 or 100%. In an aspect, the anti-pathogen activity is enhanced based on spectrum or level of activity, level of stability and/or ability to induce permeabilization compared to NsD1 or NsD2 prior to modification.

In an embodiment, the loop region on the Class II defensin is substituted by X₁ X₂ X₃ X₄ X₅ X₆ (SEQ ID NO:55) wherein:

X₁ is N, H, Q, D, K or E;

X₂ is R, H, T, K or G;

X₃ is F, H, Y or W;

X₄ is P, K, S or R;

X₅ is G or F; and/or

X₆ is P, V, I or N,

wherein the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆ does not correspond to an amino acid sequence of the Loop 1B region from the Class II solanaceous defensin prior to modification.

Insofar as the backbone defensin is NaD1, then the Loop 1B may be modified, wherein the modification comprises:

the N is substituted with an amino acid residue selected from A, R, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y and V or a naturally occurring modified form thereof;

the T is substituted with an amino acid residue selected from A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, W, Y and V or a naturally occurring modified form thereof;

the F is substituted with an amino acid residue selected from A, R, N, D, C, Q, E, G, H, I, L, K, M, P, S, T, W, Y and V or a naturally occurring modified form thereof;

the P is substituted with an amino acid residue selected from A, R, N, D, C, Q, E, G, H, I, L, K, M, F, S, T, W, Y and V or a naturally occurring modified form thereof;

the G is substituted with an amino acid residue selected from A, R, N, D, C, Q, E, H, I, L, K, M, F, P, S, T, W, Y and V or a naturally occurring modified form thereof; and/or

the I is substituted by an amino acid residue selected from A, R, N, D, C, Q, E, G, H, L, K, M, F, P, S, T, W, Y and V or a naturally occurring modified form thereof, (See also SEQ ID NO:1)

wherein the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆ does not correspond to an amino acid sequence of the Loop 1B region from NaD1.

Insofar as the backbone defensin is NaD1, then the Loop 1B may be modified, wherein the modification comprises one or more of:

the N substituted with an amino acid residue selected from G, D, H, K, A, E, Q, T, P, L, M, S, T and R;

the T substituted with an amino acid residue selected from K, R, G, H, L, N, F, I, S and Y;

the F substituted with an amino acid residue selected from W, Y, H, L, G and P;

the P substituted with an amino acid residue selected from K, S, R, H, T, E, V, N, Q, D or G;

the G substituted with an amino acid residue selected from S, K, Y, F and H; and/or

the I substituted by an amino acid residue selected from P, V, L, T, A, F, N, K, R, M, G, H and Y. See also SEQ ID NO:87.

In an embodiment, X₁ X₂ X₃ X₄ X₅ X₆ comprises an amino acid residue selected from:

X₁ is an amino acid selected from the list consisting of: L, F, S, I, A, H, Y, Q, D, K, G;

X₂ is an amino acid selected from the list consisting of: S, V, F, I, K, L, A, P, N, T, R, H, G;

X₃ is an amino acid selected from the list consisting of: A, F, W, N, I, S, Y, P, L, H;

X₄ is an amino acid selected from the list consisting of: K, G, E, R, A, P, F, Q, V, S;

X₅ is an amino acid selected from the list consisting of: M, G, K, D, S, Y, P, E, N, F; and

X₆ is an amino acid selected from the list consisting of: V, T, M, S, W, A, P, G, E, K, L, H, I, N. See also SEQ ID NO:56.

By “one or more” of X₁ through X₆ means 1 or 2 or 3 or 4 or 5 or all 6 amino acid residues are modified. A mutation outside the Loop 1B region includes, if present, from 1 to about 50 amino acid substitutions, additions and/or deletions.

Reference to a “pathogen” includes a fungus, microorganism including a bacterium, an insect, an arachnid, a virus and a nematode as well as a protozoan. In an embodiment, the pathogen is a fungus or an insect.

Reference to a “fungus” includes fungi which infect and are otherwise pathogens of plants or animals. Animal fungal pathogens include mammalian including human fungal pathogens. Particular fungal pathogens include Colletotrichum graminicola, Diplodia maydis, Fusarium graminearum and Fusarium verticilloides. Specific pathogens for the major crops include: Corn: Gibberella zeae (Fusarium graminearum), Colletotrichum graminicola, Stenocarpella maydi (Diplodia maydis), Fusarium moniliforme var. subglutinans, Fusarium verticilloides, Bipolaris maydis O, T (Cochliobolis heterostrophus), Exserohilum turcicum I, II and III, Cercospora zeae-maydis, Pythium irregulare, Pythium debaryanum, Pythium graminicola, Pythium splendens, Pythium ultimum, Pythium aphanidermatum, Aspergillus spp, Aspergillus flavus, Helminthosporium carbonum I, II and III (Cochliobolus carbonum), Helminthosporium pedicellatum, Physoderma maydis, Phyllosticta maydis, Kabatiella maydis, Cercospora sorghi, Ustilago maydis, Ustilago zeae, Puccinia sorghi, Puccinia polysora, Macrophomina phaseolina, Penicillium oxalicum, Nigrospora oryzae, Cladosporium herbarium, Curvularia lunata, Curvularia inaequalis, Curvularia pallescens, Trichoderma viride, Claviceps sorghi, Diplodia macrospora, Sclerophthora macrospora, Peronosclerospora sorghi, Peronosclerospora philippinensis, Peronosclerospora maydis, Peronosclerospora sacchari, Sphacelotheca reiliana, Physopella zeae, Cephalosporum maydis, Cephalosporum acremonium; Soybeans: Fusarium virgululiforme, Fusarium solani, Sclerotinia sclerotiorum, Fusarium oxysporum, Fusarium tucumaniae, Phakopsora pachyrhizi, Phytophthora megasperma f. sp. glycinea, Phytophthora sojae, Macrophomina phaseolina, Rhizoctonia solani, Sclerotinia sclerotiorum, Diaporthe phaseolorum var. sojae (Phomopsis sojae), Diaporthe phaseolorum var. caulivora, Sclerotium rolfsii, Cercospora kikuchii, Cercospora sojina, Peronospora manshurica, Colletotrichum dematium (Colletotrichum truncatum), Corynespora cassiicola, Septoria glycines, Phyllosticta sojicola, Alternaria alternata, Microsphaera diffusa, Fusarium semitectum, Phialophora gregata, Glomerella glycines, Pythium aphanidermatum, Pythium ultimum, Pythium debaryanum; Canola: Albugo candida, Alternaria brassicae, Leptosphaeria maculans, Rhizoctonia solani, Sclerotinia sclerotiorum, Mycosphaerella brassicicola, Pythium ultimum, Peronospora parasitica, Fusarium oxysporum, Fusarium avenaceum, Fusarium roseum, Alternaria alternata; Cotton: Fusarium oxysporum f. sp. vasinfectum, Verticillium dahliae, Thielaviopsis basicola, Alternaria macrospora, Cercospora gossypina, Phoma exigua (Ascochyta gossypii), Pythium spp Rhizoctonia solani, Puccinia scheddardii, Puccinia cacabata, Phymatotrichopsis omnivore; Canola: Leptosphaeria maculans, Sclerotinia sclerotiorum, Alternaria brassicae, Alternaria brasicicola, Plasmodiophora brassicae, Rhizoctonia solani, Fusarium spp, Pythium spp, Phytophthora spp, Alternaria spp, Peronospora parasitica, Mycosphaerella capsellae (Pseudocercosporella capsellae), Albugo candida, Phytophtohora megasperma var. megasperma, Botrytis cinerea, Erysiphe cruciferarum; Wheat: Cochliobolus sativus, Drechslera wirreganensis, Mycosphaerella graminicola, Phaeosphaeria avenaria f. sp. triticea, Phaeosphaeria nodorum, Blumeria graminis f. sp. tritici, Urocystis agropyri, Alternaria alternata, Cladosporium herbarum, Fusarium graminearum, Fusarium avenaceum, Fusarium culmorum, Fusarium pseudograminearum, Ustilago tritici, Ascochyta tritici, Cephalosporium gramineum, Colletotrichum graminicola, Erysiphe graminis f. sp. tritici, Puccinia graminis f. sp. tritici, Puccinia recondita f. sp. tritici, Puccinia striiformis, Puccinia triticina, Sclerophthora macrospora, Urocystis agropyri, Pyrenophora tritici-repentis, Pyrenophora semeniperda, Phaeosphaeria nodorum, Septoria nodorum, Septoria tritici, Septoria avenae, Pseudocercosporella herpotrichoides, Rhizoctonia solani, Rhizoctonia cerealis, Gaeumannomyces graminis var. tritici, Pythium spp, Pythium aphanidermatum, Pythium arrhenomannes, Pythium gramicola, Pythium ultimum, Bipolaris sorokiniana, Claviceps purpurea, Tapesia yallundae, Tilletia tritici, Tilletia laevis, Tilletia caries, Tilletia indica, Ustilago tritici, Wojnowicia graminis, Cochliobolus sativus; Sorghum: Exserohilum turcicum, Colletotrichum sublineolum, Cercospora sorghi, Gloeocercospora sorghi, Ascochyta sorghina, Puccinia purpurea, Macrophomina phaseolina, Perconia circinata, Fusarium mondiforme, Alternaria alternata, Bipolaris sorghicola, Helminthosporium sorghicola, Curvularia lunata, Phoma insidiosa, Ramulispora sorghi, Ramulispora sorghicola, Phyllachara saccari, Sporisorium reilianum (Sphacelotheca reiliana), Sphacelotheca cruenta, Sporisorium sorghi, Claviceps sorghi, Rhizoctonia solani, Acremonium strictum, Sclerophthona macrospora, Peronosclerospora sorghi, Peronosclerospora philippinensis, Sclerospora graminicola, Fusarium graminearum, Fusarium oxysporum, Pythium arrhenomanes, Pythium graminicola; Sunflower: Plasmopara halstedii, Sclerotinia sclerotiorum, Septoria helianthi, Phomopsis helianthi, Alternaria helianthi, Alternaria zinniae, Botrytis cinerea, Phoma macdonaldii, Macrophomina phaseolina, Erysiphe cichoracearum, Rhizopus oryzae, Rhizopus arrhizus, Rhizopus stolonifer, Puccinia helianthe, Verticillium dahliae, Cephalosporum acremonium, Phytophthora cryptogea, Albugo tragopogonis; Alfalfa: Pythium ultimum, Pythium irregulare, Pythium splendens, Pythium debaryanum, Pythium aphanidermatum, Phytophthora megasperma, Peronospora trifoliorum, Phoma medicaginis var. medicaginis, Cercospora medicaginis, Pseudopeziza medicaginis, Leptotrochila medicaginis, Fusarium oxysporum, Verticillium albo-atrum, Aphanomyces euteiches, Stemphylium herbarum, Stemphylium alfalfae, Colletotrichum trifolii, Leptosphaerulina briosiana, Uromyces striatus, Sclerotinia trifoliorum, Stagonospora meliloti, Stemphylium botryosum and Leptotrichila medicaginis.

In an embodiment, fungal pathogens in corn include Fusarium graminearum, Colletotrichum graminicola, Stenocarpella maydis, Fusarium verticilloides, Cochliobolis heterostrophus, Exserohilum turcicum, Cercospora zea-maydis.

In an embodiment, fungal pathogens in soybean include Fusarium virguliforme, Fusarium solanai, Sclerotinia sclerotiorum, Fusarium oxysporum, Fusarium tucumaniae, Phakopsora pachirhizi.

Animal including mammalian and in particular human fungal pathogens include species of Altemaeria spp, Aspergillus spp, Candida spp, Fusarium spp, Trychophyton spp, Cryptococcus spp, Microsporum spp, Penicillium spp, Trichosporon spp, Scedosporium spp, Paeciliomyces spp, Acremonium spp and Dermatiaceous molds. Specific animal, including mammalian and in particular human pathogens include Alternaria alternata, Aspergillus fumigatus, Aspergillus niger, Aspergillus flavus, Aspergillus nidulans, Aspergillus paraciticus, Candida albicans, Candida dubliniensis, Candida famata, Candida glabrata, Candida guilliermondii, Candida haemulonii, Candida kefyr, Candida krusei, Candida lusitaniae, Candida norvegensis, Candida parapsilosis, Candida tropicalis, Candida viswanathii, Fusarium oxysporum, Fusarium solani, Fusarium monoliforme, Trycophyton rubrum, Trycophyton mentagrophytes, Trycophyton interdigitales, Trycophyton tonsurans, Cryptococcus neoformans, Cryptococcus gattii, Cryptococcus grubii, Microsporum canis, Microsporum gypseum, Penicillium mameffei, Tricosporon beigelii, Trichosporon asahii, Trichosporon inkin, Trichosporon asteroides, Trichosporon cutaneum, Trichosporon domesticum, Trichosporon mucoides, Trichosporon ovoides, Trichosporon pullulans, Trichosporon loubieri, Trichosporon japonicum, Scedosporium apiospermum, Scedosporium prolificans, Paecilomyces variotii, Paecilomyces lilacinus, Acremonium stricutm, Cladophialophora bantiana, Wangiella dermatitidis, Ramichloridium obovoideum, Chaetomium atrobrunneum, Dactlaria gallopavum, Bipolaris spp, Exserohilum rostratum as well as Absidia corymbifera, Apophysomyces elegans, Mucor indicus, Rhizomucor pusillus, Rhizopus oryzae, Cunninghamella bertholletiae, Cokeromyces recurvatus, Saksenaea vasiformis, Syncephalastrum racemosum, Basidiobolus ranarum, Conidiobolus coronatus/Conidiobolus incongruus, Blastomyces dermatitidis, Coccidioides immitis, Coccidioides posadasii, Histoplasma capsulatum, Paracoccidioides brasiliensis, Pseudallescheria boydii and Sporothrix schenckii.

Reference to a “fungus” also includes oomycetes such as Pythium spp and Phytophthora spp. The term “fungus” also encompasses a rust.

Bacterial pathogens include Xanthomonas spp and Pseudomonas spp. Other microorganisms include Phytoplasma spp and Spiroplasma spp. Other pathogens include viruses, nematodes and protozoa. Insect pathogens include Diatraea grandiosella, Ostrinia nubialis, Rhopalosiphum spp, Helicoverpa spp, Plutella xylostella and Lygus spp.

Also provided herein are isolated nucleic acid molecules encoding the modified Class II solanaceous defensin. In an embodiment, the nucleic acid comprises a nucleotide sequence which encodes an amino acid sequence set forth SEQ ID NO:57. In an embodiment, the nucleic acid comprises a nucleotide sequence which encodes an amino acid sequence set forth SEQ ID NO:84.

Hence, an isolated nucleic acid molecule is provided encoding an artificially created defensin comprising:

(i) an amino acid backbone derived from or corresponding to a Class II solanaceous defensin;

(ii) a Loop 1B on the backbone or its equivalent being subjected to one or more of: (a) an amino acid substitution, addition and/or deletion; and/or (b) replacement of all or part by Loop 1B or a modified form thereof from another defensin; and optionally (c) another an amino acid substitution, addition and/or deletion outside the Loop 1B region on the backbone;

wherein the artificially created defensin exhibits anti-pathogen activity Loop 1B.

Another aspect taught herein is an isolated nucleic acid molecule encoding an artificially created defensin comprising a backbone amino acid sequence from a Class II solanaceous defensin having a loop region between β-strand 1 and the α-helix on the N-terminal end portion of the Class II solanaceous defensin wherein the loop region is modified by an amino acid substitution, addition and/or deletion to generate a defensin which has anti-pathogen activity.

In an aspect, the loop region is Loop 1B. Another aspect is directed to an isolated nucleic acid molecule encoding an artificially created defensin comprising a backbone amino acid sequence from a Class II solanaceous defensin having a Loop 1B region between 3-strand 1 and the α-helix on the N-terminal end portion of the Class II solanaceous defensin, the defensin selected from the list consisting of NaD1, NsD1, NsD2, PhD1, PhD2, TPP3, FST, NeThio1, NeThio2, NpThio1, Na-gth, Cc-gth, C20 and SL549 wherein the Loop 1B region is modified by an amino acid substitution, addition and/or deletion to generate a region comprising the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆, (SEQ ID NO:86) wherein each of X₁ through X₆ is an amino acid residue and wherein X₁ is N, G, D, H, K, A, E, Q, T, P, L, M, S, or R; X₂ is K, R, G, H, L, N, F, I, S, T or Y; X₃ is W, Y, H, L, G, F or P; X₄ is P, K, S, R, H, T, E, V, N, Q, D or G; X₅ is S, K, Y, F, G or H; and/or X₆ is P, V, L, T, A, F, N, K, R, M, G, H or Y; wherein the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆ does not correspond to an amino acid sequence of the Loop 1B region from the Class II solanaceous defensin prior to modification to thereby artificially generate a defensin which has anti-pathogen activity. In an embodiment, X₁ X₂ X₃ X₄ X₅ X₆ (SEQ ID NO:56) comprises an amino acid residue selected from L, F, S, I, A, H, Y, Q, D, K, G; X₂ is an amino acid selected from the list consisting of: S, V, F, I, K, L, A, P, N, T, R, H, G; X₃ is an amino acid selected from the list consisting of: A, F, W, N, I, S, Y, P, L, H; X₄ is an amino acid selected from the list consisting of: K, G, E, R, A, P, F, Q, V, S; X₅ is an amino acid selected from the list consisting of: M, G, K, D, S, Y, P, E, N, F; and X₆ is an amino acid selected from the list consisting of: V, T, M, S, W, A, P, G, E, K, L, H, I, N.

Another aspect is directed to an isolated nucleic acid molecule encoding an artificially created defensin comprising a backbone amino acid sequence from a Class II solanaceous defensin having a Loop 1B region between β-strand 1 and the α-helix on the N-terminal end portion of the Class II solanaceous defensin, the defensin having a C-terminal end amino acid sequence of the mature domain with at least 70% similarity to SEQ ID NO:52, wherein the Loop 1B region is modified by an amino acid substitution, addition and/or deletion to generate a region comprising the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆, SEQ ID NO:1, wherein each of X₁ through X₆ is an amino acid residue and wherein X₁ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof; X₂ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof; X₃ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof; X₄ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V; X₅ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof; and/or X₆ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof; wherein the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆ does not correspond to an amino acid sequence of the Loop 1B region from the Class II solanaceous defensin prior to modification, to thereby artificially generate a defensin which has anti-pathogen activity.

Another aspect is an isolated nucleic acid molecule encoding an artificially created defensin having a backbone amino acid sequence derived from a Nicotiana suaveolens defensin with a Loop 1B region or its equivalent modified by a single or multiple amino acid substitution, addition and/or deletion to generate a region comprising the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆, SEQ ID NO:1, wherein each of X₁ through X₆ is an amino acid residue and X₁ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof; X₂ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof; X₃ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof; X₄ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof; X₅ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof; and/or X₆ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof; wherein the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆ does not correspond to an amino acid sequence of the Loop 1B region from the Class II solanaceous defensin prior to modification to artificially generate a defensin which has anti-pathogen activity. Examples of defensins for N. suaveolens include NsD1 and NsD2.

Still another aspect provides an isolated nucleic acid molecule encoding an artificially created defensin having a backbone amino acid sequence derived from a Nicotiana suaveolens defensin with a Loop 1B region or its equivalent modified by a single or multiple amino acid substitution, addition and/or deletion to generate a region comprising the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆, SEQ ID NO:86, wherein each of X₁ through X₆ is an amino acid residue and X₁ is N, G, D, H, K, A, E, Q, T, P, L, M, S, or R; X₂ is K, R, G, H, L, N, F, I, S, T or Y; X₃ is W, Y, H, L, G, F or P; X₄ is P, K, S, R, H, T, E, V, N, Q, D or G; X₅ is S, K, Y, F, G or H; and/or X₆ is P, V, L, T, A, F, N, K, R, M, G, H, I or Y; wherein the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆ does not correspond to an amino acid sequence of the Loop 1B region from the Class II solanaceous defensin prior to modification to artificially generate a defensin which has anti-pathogen activity. Examples of defensins for N. suaveolens include NsD1 and NsD2.

In yet another embodiment, the isolated nucleic acid molecule encodes an artificially created defensin comprising a backbone amino acid sequence from a Class II solanaceous defensin having a Loop 1B region between β-strand 1 and the α-helix on the N-terminal end portion of the solanaceous defensin, the defensin selected from the list consisting of NaD1, NsD1, NsD2, PhD1, PhD2, TPP3, FST, NeThio1, NeThio2, NpThio1, Na-gth, Cc-gth, C20 and SL549 wherein the Loop 1B region on the Class II solanaceous defensin backbone is replaced with a Loop 1B region from a defensin selected from the list consisting of NaD2 (SEQ ID NO:29)(HRFKGP), Zea2 (SEQ ID NO:30)(QHHSFP), PsD1 (SEQ ID NO:31)(DTYRGV)), MsDef1 (SEQ ID NO:33)(DKYRGP), SoD2 (SEQ ID NO:34)(KTFKGI) and DmAMP1 (SEQ ID NO:35)(KTWSGN) or a Loop 1B sequence selected from SEQ ID NO:67 to 79 to generate a defensin which has anti-pathogen activity.

The term “similarity” as used herein includes exact identity between compared sequences at the nucleotide or amino acid level. Where there is non-identity at the nucleotide level, “similarity” includes differences between sequences which result in different amino acids that are nevertheless related to each other at the structural, functional, biochemical and/or conformational levels. Where there is non-identity at the amino acid level, “similarity” includes amino acids that are nevertheless related to each other at the structural, functional, biochemical and/or conformational levels. In a particularly preferred embodiment, nucleotide and sequence comparisons are made at the level of identity rather than similarity.

Terms used to describe sequence relationships between two or more polynucleotides or polypeptides include “reference sequence”, “comparison window”, “sequence similarity”, “sequence identity”, “percentage of sequence similarity”, “percentage of sequence identity”, “substantially similar” and “substantial identity”. A “reference sequence” is at least 12 but frequently 15 to 18 and often at least 25 or above, such as 30 monomer units, inclusive of nucleotides and amino acid residues, in length. Because two polynucleotides may each comprise (1) a sequence (i.e. only a portion of the complete polynucleotide sequence) that is similar between the two polynucleotides, and (2) a sequence that is divergent between the two polynucleotides, sequence comparisons between two (or more) polynucleotides are typically performed by comparing sequences of the two polynucleotides over a “comparison window” to identify and compare local regions of sequence similarity. A “comparison window” refers to a conceptual segment of typically 12 contiguous residues that is compared to a reference sequence. The comparison window may comprise additions or deletions (i.e. gaps) of about 20% or less as compared to the reference sequence (which does not comprise additions or deletions) for optimal alignment of the two sequences. Optimal alignment of sequences for aligning a comparison window may be conducted by computerized implementations of algorithms (GAP, BESTFIT, FASTA, and TFASTA in the Wisconsin Genetics Software Package Release 7.0, Genetics Computer Group, 575 Science Drive Madison, Wis., USA) or by inspection and the best alignment (i.e. resulting in the highest percentage homology over the comparison window) generated by any of the various methods selected. Reference also may be made to the BLAST family of programs as for example disclosed by Altschul et al. (1997) Nucl. Acids. Res. 25: 3389). A detailed discussion of sequence analysis can be found in Unit 19.3 of Ausubel et al. (1998) In: Current Protocols in Molecular Biology, John Wiley & Sons Inc. 1994-1998.

The terms “sequence similarity” and “sequence identity” as used herein refers to the extent that sequences are identical or functionally or structurally similar on a nucleotide-by-nucleotide basis or an amino acid-by-amino acid basis over a window of comparison. Thus, a “percentage of sequence identity”, for example, is calculated by comparing two optimally aligned sequences over the window of comparison, determining the number of positions at which the identical nucleic acid base (e.g. A, T, C, G, I) or the identical amino acid residue (e.g. Ala, Pro, Ser, Thr, Gly, Val, Leu, Ile, Phe, Tyr, Trp, Lys, Arg, His, Asp, Glu, Asn, Gln, Cys and Met) occurs in both sequences to yield the number of matched positions, dividing the number of matched positions by the total number of positions in the window of comparison (i.e., the window size), and multiplying the result by 100 to yield the percentage of sequence identity. For the purposes of the present disclosure, “sequence identity” will be understood to mean the “match percentage” calculated by the DNASIS computer program (Version 2.5 for windows; available from Hitachi Software engineering Co., Ltd., South San Francisco, Calif., USA) using standard defaults as used in the reference manual accompanying the software. Similar comments apply in relation to sequence similarity. By “at least 70%” means 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99 and 100%.

The instant disclosure extends to nucleic acid molecules which hybridize under low stringency conditions to the nucleic acid molecule encoding the modified defensin.

Stringency conditions can be defined by, for example, the concentrations of salt or formamide in the pre-hybridization and hybridization solutions, or by the hybridization temperature, and are well known in the art. For example, stringency can be increased by reducing the concentration of salt, increasing the concentration of formamide, or raising the hybridization temperature, altering the time of hybridization, as described in detail, below. In alternative aspects, nucleic acids of the present disclosure are defined by their ability to hybridize under various stringency conditions (e.g. high, medium, and low).

Reference herein to a “low stringency” includes and encompasses from at least about 0 to at least about 15% v/v formamide and from at least about 1 M to at least about 2 M salt for hybridization, and at least about 1 M to at least about 2 M salt for washing conditions. Generally, low stringency is at from about 25-30° C. to about 42° C. The temperature may be altered and higher temperatures used to replace formamide and/or to give alternative stringency conditions. Alternative stringency conditions may be applied where necessary, such as “medium stringency”, which includes and encompasses from at least about 16% v/v to at least about 30% v/v formamide and from at least about 0.5 M to at least about 0.9 M salt for hybridization, and at least about 0.5 M to at least about 0.9 M salt for washing conditions, or “high stringency”, which includes and encompasses from at least about 31% v/v to at least about 50% v/v formamide and from at least about 0.01 M to at least about 0.15 M salt for hybridization, and at least about 0.01 M to at least about 0.15 M salt for washing conditions. In general, washing is carried out T_(m)=69.3+0.41 (G+C) % (Marmur and Doty (1962) J Mol Biol 5:109-118). However, the T_(m) of a duplex nucleic acid molecule decreases by 1° C. with every increase of 1% in the number of mismatch base pairs (Bonner and Laskey (1974) Eur J Biochem 46:83-88). Formamide is optional in these hybridization conditions. Accordingly, particularly preferred levels of stringency are defined as follows: low stringency is 6×SSC buffer, 0.1% w/v SDS at 25-42° C.; a moderate stringency is 2×SSC buffer, 0.1% w/v SDS at a temperature in the range 20° C. to 65° C.; high stringency is 0.1×SSC buffer, 0.1% w/v SDS at a temperature of at least 65° C.

The terms “sequence similarity” and “sequence identity” as used herein refer to the extent that sequences are identical or functionally or structurally similar on a nucleotide-by-nucleotide basis or an amino acid-by-amino acid basis over a window of comparison. Thus, a “percentage of sequence identity”, for example, is calculated by comparing two optimally aligned sequences over the window of comparison, determining the number of positions at which the identical nucleic acid base (e.g. A, T, C, G, I) or the identical amino acid residue (e.g. Ala, Pro, Ser, Thr, Gly, Val, Leu, Ile, Phe, Tyr, Trp, Lys, Arg, His, Asp, Glu, Asn, Gln, Cys and Met) occurs in both sequences to yield the number of matched positions, dividing the number of matched positions by the total number of positions in the window of comparison (i.e. the window size), and multiplying the result by 100 to yield the percentage of sequence identity. For the purposes of the present disclosure, “sequence identity” will be understood to mean the “match percentage” calculated by the DNASIS computer program (Version 2.5 for windows; available from Hitachi Software engineering Co., Ltd., South San Francisco, Calif., USA) using standard defaults as used in the reference manual accompanying the software. Similar comments apply in relation to sequence similarity.

The nucleic acid molecules taught herein are also capable of hybridizing to other genetic molecules. Reference herein to “hybridizes” refers to the process by which a nucleic acid strand joins with a complementary strand through base pairing. Hybridization reactions can be sensitive and selective so that a particular sequence of interest can be identified even in samples in which it is present at low concentrations. Stringent conditions can be defined by, for example, the concentrations of salt or formamide in the prehybridization and hybridization solutions, or by the hybridization temperature, and are well known in the art. For example, stringency can be increased by reducing the concentration of salt, increasing the concentration of formamide, or raising the hybridization temperature, altering the time of hybridization, as described in detail, below. In alternative aspects, the present nucleic acids are defined by their ability to hybridize under various stringency conditions (e.g. high, medium, and low).

The isolated nucleic acid molecule may also be in a vector including an expression or transfer vector suitable for use in plant cells, microbial cells and non-human animal cells. Reference to a “vector” includes a multi-gene expression vector (MGEV) such as described by PCT/AU02/00123.

In accordance with the latter aspect, there is provided a multigene expression vehicle (MGEV) comprising a polynucleotide having 2 to 8 domain segments each domain encoding a functional protein, each domain being joined to the next in a linear sequence by a linker segment, the domain and segments all being in the same reading frame, and wherein at least one of the domains is a modified Class II solanaceous defensin as described herein. In an embodiment, at least one other domain is a proteinase inhibitor or precursor thereof. In yet another embodiment, at least one domain is a modified Class II solanaceous defensin as contemplated herein, and at least one domain is a proteinase inhibitor or precursor form thereof. By “proteinase inhibitor” includes a serine proteinase inhibitor and a cysteine proteinase inhibitor.

The nucleic acid sequence encoding the modified defensin may be incorporated into a DNA construct or vector in combination with suitable regulatory sequences (promoter, terminator, transit peptide, etc). The nucleic acid may also be operably linked to a heterologous promoter. For some applications, the nucleic acid sequence encoding the modified defensin may be inserted within a coding region expressing another protein to form a defensin fusion protein or may be used to replace a domain of a protein to give that protein anti-pathogen activity. The nucleic acid sequence may be placed under the control of a homologous or heterologous promoter which may be a constitutive or an inducible promoter (stimulated by, for example, environmental conditions, presence of a pathogen, presence of a chemical). The transit peptide may be homologous or heterologous to the modified defensin and is chosen to ensure secretion to the desired organelle or to the extracellular space. The transit peptide may be naturally associated with a particular defensin. Such a DNA construct may be cloned or transformed into a biological system which allows expression of the encoded modified defensin or an active part of the defensin. Suitable biological systems include microorganisms (for example, the Pichia pastoris expression system, Escherichia coli, Pseudomonas, endophytes such as Clavibacter xyli subsp. cynodontis (Cxc); yeast; viruses; bacteriophages; etc), cultured cells (such as insect cells, mammalian cells) and plants. In some cases, the expressed defensin is subsequently extracted and isolated for use.

The modified defensin taught herein is useful for combating pathogen diseases in plants and animals including mammals such as humans. Hence, the modified Class II solanaceous defensins have horticultural and agricultural applications as well as applications as medicaments for animal including mammalian such as human use. Further provided is a process of combating pathogens whereby they are exposed to the modified defensin herein described. The modified defensin may be used in the form of a composition. The modified defensin may be used alone or in combination with a chemical pathogenicide, an anti-pathogen protein and/or a Type II serine or cysteine proteinase inhibitor or precursor form thereof.

Whilst the modified defensin herein described is useful for protecting plants against pathogen infestation, growth, maintenance or spread, the modified defensin also has application as medicaments, including topical medicaments, for non-plants such as animals including mammals such as humans.

Hence, another aspect taught herein is a composition comprising the modified defensin as described herein together with one or more pharmaceutically or veterinarilly or horticulturally acceptable carriers, diluents or excipients and/or one or more other anti-pathogen agents such as a chemical pathogenicide, a proteinaceous anti-pathogen agent and/or a proteinase inhibitor or a precursor form thereof. In an embodiment, the composition is in the form of a spray, mist, micro- or nano-particles, aqueous solution, powder, cream, ointment, gel, impregnated bandage, liquid, formulation, paint or other suitable distribution medium including oral forms of the composition.

For pharmaceutical applications, the modified defensin (including any product derived from it) may be used as a pathogenicide or a pathogenostat to treat mammalian infections (for example, to combat yeasts such as Candida).

The modified defensin (including any product derived from it) according to the present disclosure may also be used as a preservative (for example, as a food additive) or as part of a soil or growth medium preparation program.

For agricultural applications, the modified defensin may be used to improve the disease-resistance or disease-tolerance of crops either during the life of the plant or for post-harvest crop protection. Pathogens exposed to the peptides are inhibited. The modified defensin may eradicate a pathogen already established on the plant or may protect the plant from future pathogen attack. The eradicant effect of the peptide is particularly advantageous. Reference to a “plant” includes a crop plant such as sorghum, wheat, barley, maize, cotton, rice, canola, corn, abaca, alfalfa, almond, apple, asparagus, banana, bean-phaseolus, blackberry, broad bean, cashew, cassava, chick pea, citrus, coconut, coffee, fig, flax, grapes, groundnut, hemp, lavender, mushroom, olive, onion, pea, peanut, pear, pearl millet, potato, rapeseed, ryegrass, soybean, strawberry, sugar beet, sugarcane, sunflower, sweetpotato, taro, tea, tobacco, tomato, triticale, truffle and yam.

Exposure of a plant pathogen to the modified defensin may be achieved in various ways, for example:

(a) The modified defensin may be applied to plant parts or to the soil or other growth medium surrounding the roots of the plants or to the seed of the plant before it is sown using standard agricultural techniques (such as spraying). The defensin may have been chemically synthesized or extracted from microorganisms or plants genetically modified to express the protein. The protein may be applied to plants or to the plant growth medium in the form of a composition comprising the defensin in admixture with a solid or liquid diluent and optionally various adjuvants such as surface-active agents. Solid compositions may be in the form of dispersible powders, granules, or grains.

(b) A composition comprising a microorganism genetically modified to express the anti-pathogen defensin may be applied to a plant or the soil in which a plant grows.

(c) An endophyte genetically modified to express the anti-pathogen defensin may be introduced into the plant tissue (for example, via a seed treatment process). An endophyte is defined as a microorganism having the ability to enter into non-pathogenic endo symbiotic relationships with a plant host. A method of endophyte-enhanced protection of plants has been described in a series of patent applications by Crop Genetics International Corporation (for example, International Application Publication Number W090/13224, European Patent Publication Number EP-125468-B1, International Application Publication Number W091/10363, International Application Publication Number W087/03303). The endophyte may be genetically modified to produce agricultural chemicals. International Patent Application Publication Number W094/16076 (ZENECA Limited) describes the use of endophytes which have been genetically modified to express a plant-derived anti-fungal peptide.

(d) DNA encoding an anti-pathogen defensin may be introduced into the plant genome so that the peptide is expressed within the plant body (the DNA may be cDNA, genomic DNA or DNA manufactured using a standard nucleic acid synthesizer).

For compositions comprising the modified defensin described herein, generally include a carrier, excipient, diluent, preservative, stabilizer and/or a solid or liquid additive. Optionally, another anti-pathogenic agent is also included.

The composition may take a wide variety of forms depending on the intended method of administration. Generally, but not exclusively, topical compositions are used for plant and animals. In preparing the compositions, usual media may be employed such as, for example, water, glycols, oils, alcohols, preservatives and/or coloring agents. The compositions may take the form of a liquid preparation such as, for example, suspensions, elixirs and solutions. Carriers such as starches, sugars, microcrystalline cellulose, diluents, granulating agents, lubricants, binders, disintegrating agents and the like may also be used. The composition may also be in the form of a power, capsule and tablet.

The modified defensins herein may be administered directly to a plant or part thereof or to the root system or soil or medium surrounding the root system or to the skin, hair or fur of an animal including a mammal such as a human.

When administered by aerosol or spray, the compositions are prepared according to techniques well-known in the art of agricultural and pharmaceutical formulation and may be prepared as solutions in saline, employing benzyl alcohol or other suitable preservatives, absorption promoters to enhance bioavailability, fluorocarbons and/or other solubilizing or dispersing agents known in the art.

The effective dosage of the modified defensins may vary depending on the particular defensin employed, the mode of administration, the pathogen being treated and the severity of the pathogen infestation. Thus, the dosage regimen utilizing the modified defensin is selected in accordance with a variety of factors including type, species, age, weight, sex and medical condition of the plant or subject; the severity of the condition to be treated; the route of administration; and the particular defensin thereof employed. A horticulturist, physician, clinician or veterinarian of ordinary skill can readily determine and prescribe the effective amount of the defensin required to prevent, counter or arrest the progress of pathogen infestation. Slow release formulations are also contemplated herein.

Dragee cores are provided with suitable coatings. For this purpose, concentrated sugar solutions may be used, which may optionally contain gum arabic, talc, polyvinyl pyrrolidone, carbopol gel, polyethylene glycol and/or titanium dioxide, lacquer solutions, and suitable organic solvents or solvent mixtures. Dyestuffs or pigments may be added to the tablets or dragee coatings for identification or to characterize different combinations of active compound doses.

Defensin preparations include push-fit capsules made of gelatin, as well as soft, sealed capsules made of gelatin and a plasticizer, such as glycerol or sorbitol. The push-fit capsules can contain the active ingredients in admixture with filler such as lactose, binders such as starches and/or lubricants such as talc or magnesium stearate and, optionally, stabilizers. In soft capsules, the active compounds may be dissolved or suspended in suitable liquids, such as fatty oils, liquid paraffin, or liquid polyethylene glycols. In addition, stabilizers may be added.

The modified defensin composition or expression vector encoding same may also comprise another anti-pathogen substance such as another defensin or an anti-pathogen protein or peptide, or a chemical pathogenicide or a proteinase inhibitor or precursor from thereof.

Another aspect taught herein includes a protocol or method for treating or preventing a plant infested with a pathogen, the protocol or method comprising applying to the plant or part thereof or to the soil or growth support medium around the plant an anti-pathogen effective amount of a composition comprising the modified defensin as described herein, alone or together with another anti-pathogen agent.

Another aspect provides a protocol or method for treating or preventing an animal including a mammalian such as a human subject infected or infested with a pathogen, the protocol or method comprising applying to the subject an anti-pathogen effective amount of a composition comprising the modified defensin as described herein.

The term “applying” includes contacting and exposing. The modified defensin may be used alone or together with other anti-pathogen agents or agents which facilitate the modified defensin accessing a pathogen.

In a further embodiment, plant cells may be transformed with recombinant DNA constructs according to a variety of known methods (Agrobacterium Ti plasmids, electroporation, microinjection, microprojectile gun, etc). The transformed cells may in suitable cases be regenerated into whole plants in which the new nuclear material is stably incorporated into the genome. Both transformed monocotyledonous and dicotyledonous plants may be obtained in this way, although the latter are usually regenerated more easily. Some of the progeny of these primary transformants inherit the recombinant DNA encoding the anti-pathogen defensin.

The present disclosure further provides a plant having improved resistance to a pathogen and containing recombinant DNA which expresses a modified Class II solanaceous defensin. Such a plant may be used as a parent in standard plant breeding crosses to develop hybrids and lines having pathogen including fungal resistance.

Recombinant DNA is DNA, generally heterologous, which has been introduced into the plant or its ancestors by transformation. The recombinant DNA encodes a modified Class II solanaceous defensin expressed for delivery to a site of pathogen attack (such as the leaves).

Where the present modified defensin is expressed within a transgenic plant or its progeny, the pathogen is exposed to the defensin at the site of or remote to the site of pathogen attack on the plant. In particular, by use of appropriate gene regulatory sequences, the defensin may be produced in vivo when and where it will be most effective. For example, the defensin may be produced within parts of the plant where it is not normally expressed in quantity but where disease resistance is important (such as in the leaves).

Examples of genetically modified plants which may be produced include field crops, cereals, fruit and vegetables such as: corn, soybean, sorghum, wheat, barley, maize, cotton, canola, rice, abaca, alfalfa, almond, apple, asparagus, banana, bean-phaseolus, blackberry, broad bean, canola, cashew, cassava, chick pea, citrus, coconut, coffee, fig, flax, grapes, groundnut, hemp, lavender, mushroom, olive, onion, pea, peanut, pear, pearl millet, potato, rapeseed, ryegrass, strawberry, sugar beet, sugarcane, sunflower, sweetpotato, taro, tea, tobacco, tomato, triticale, truffle and yam.

A pathogen may be any pathogen growing on, in or near the plant. In this context, resistance includes an enhanced tolerance to a pathogen when compared to a wild-type plant. Resistance may vary from a slight increase in tolerance to the effects of the pathogen (where the pathogen in partially inhibited) to total resistance so that the plant is unaffected by the presence of pathogen (where the pathogen is severely inhibited or killed). An increased level of resistance against a particular pathogen or resistance against a wider spectrum of pathogens may both constitute an improvement in resistance. Transgenic plants (or plants derived therefrom) showing improved resistance are selected following plant transformation or subsequent crossing.

The present disclosure provides a method for generating a genetically modified plant or its progeny which exhibit anti-pathogen activity, the method comprising creating a plant which comprises cells which express the nucleic acid encoding a modified defensin, as taught herein the level of expression sufficient for the modified defensin to exhibit a protective effect against plant pathogens.

The present modified defensins may be used alone or in combination with one or more other defensins from any group of the defensins. Hence, provided herein is a method for generating plant exhibiting anti-pathogen properties, the method comprising creating a genetically modified plant or its progeny which comprises cells which express the modified Class II solanaceous defensin taught herein in combination with another defensin. Such a plant has reduced risk of promoting resistance by pathogens. Reference to “synergy” includes the combatting of resistance to a single defensin by using two or more defensins.

The present modified defensin may be manufactured based on its amino acid sequence using standard stepwise addition of one or more amino acid residues using, for example, a peptide or protein synthesizer. Alternatively, the modified defensin may be made by recombinant means. The modified defensin may be used alone or in combination with other anti-pathogen agents whether provided by a cell or topically or systemically applied.

As indicated above, the present modified defensin exhibits improved or enhanced anti-pathogen activity. In a particular embodiment, the pathogen is a fungal pathogen.

Hence, in a particular embodiment, there is provided an artificially created Class II solanaceous defensin, the defensin comprising a Class II solanaceous defensin backbone with a Loop 1B region on the backbone modified by a single or multiple amino acid substitution, addition and/or deletion to generate a defensin which has anti-fungal activity wherein the backbone may optionally comprise a single or multiple amino acid substitution, addition and/or deletion elsewhere on the backbone such as in the C-terminal CTPP. The present disclosure further contemplates the use of an artificially created defensin comprising a backbone amino acid sequence from a Class II solanaceous defensin having a Loop 1B region or its equivalent loop between the first β-strand and the α-helix on the N-terminal end portion of the Class II solanaceous defensin wherein the Loop 1B region is modified by a single or multiple amino acid substitution, addition and/or deletion in the manufacture of an anti-pathogen medicament.

Furthermore, another aspect is the use of a Class II solanaceous defensin comprising a C-terminal end region having at least about 70% similarity to SEQ ID NO:52 in the manufacture of an artificially created defensin comprising a modified Loop 1B region and which artificially created defensin exhibits anti-pathogen activity.

Further provided herein is a method for reducing or controlling pathogen infestation on or in a plant or in soil surrounding a plant or its roots, the method comprising topically applying the modified defensin of the present disclosure to the plant or plant roots or to the soil. Alternatively, the method comprises generating a genetically modified plant expressing the modified defensin as well as progeny of the modified plants which contain the modified defensin.

Still another aspect provides a method for reducing or controlling pathogen infestation on or in an animal the method comprising topically applying the present modified Class II solanaceous defensin to a potentially infected surface region on the animal. In an embodiment, the animal is a mammal including a human. Hence, animal and in particular mammalian such as human anti-pathogen medicaments are contemplated herein. In an embodiment, the medicament is in the form of a powder, spray, atomizer, nanoparticle, gel, paste, impregnated bandage, paint, aerosol, drench or other liquid. The anti-pathogen formulation may also be a slow release composition. The formulation may be used to treat an infected subject or as a preventative.

As used herein, “comprising” is synonymous with “including,” “containing,” or “characterized by,” and is inclusive or open-ended and does not exclude additional, unrecited elements or method steps. As used herein, “consisting of” excludes any element, step, or ingredient not specified in the claim element. As used herein, “consisting essentially of” does not exclude materials or steps that do not materially affect the basic and novel characteristics of the claim. Any recitation herein of the term “comprising”, particularly in a description of components of a composition or in a description of elements of a device, is understood to encompass those compositions and methods consisting essentially of and consisting of the recited components or elements. The present disclosure illustratively described herein suitably may be practiced in the absence of any element or elements, limitation or limitations which is not specifically disclosed herein.

When a group of substituents is disclosed herein, it is understood that all individual members of those groups and all subgroups, including any isomers and enantiomers of the group members, and classes of compounds that can be formed using the substituents are disclosed separately. When a compound is claimed, it should be understood that compounds known in the art including the compounds disclosed in the references disclosed herein are not intended to be included. When a Markush group or other grouping is used herein, all individual members of the group and all combinations and subcombinations possible of the group are intended to be individually included in the disclosure.

When a range is recited herein, it is intended that all subranges within the stated range, and all integer values within the stated range, are intended, as if each subrange and integer value was recited.

Various aspects are encompassed by the subject specification. These aspects include the following:

1. An artificially created defensin comprising a backbone amino acid sequence from a Class II solanaceous defensin having a loop region between β-strand 1 and the α-helix on the N-terminal end portion of the Class II solanaceous defensin wherein the loop region is modified by an amino acid substitution, addition and/or deletion to generate a defensin which has anti-pathogen activity. 2. The artificially created defensin of Aspect 1 wherein the loop region is Loop 1B. 3. The artificially created defensin of Aspect 2 wherein the Loop 1B on the Class II solanaceous defensin is modified to generate the sequence X₁ X₂ X₃ X₄ X₅ X₆, SEQ ID NO:1, wherein X is an amino acid residue and wherein:

X₁ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof;

X₂ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof;

X₃ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof;

X₄ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof;

X₅ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof; and/or

X₆ is A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof;

wherein the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆ does not correspond to an amino acid sequence of the Loop 1B region from the Class II solanaceous defensin prior to modification. 4. The artificially created defensin of Aspect 3 wherein the Loop 1B on the Class II solanaceous defensin is modified to generate the sequence X₁ X₂ X₃ X₄ X₅ X₆, SEQ ID NO:86, wherein X is an amino acid residue and wherein:

X₁ is N, G, D, H, K, A, E, Q, T, P, L, M, S, or R;

X₂ is K, R, G, H, L, N, F, I, S, T or Y;

X₃ is W, Y, H, L, G, F or P;

X₄ is P, K, S, R, H, T, E, V, N, Q, D or G;

X₅ is S, K, Y, F, G or H; and/or

X₆ is P, V, L, T, A, F, N, K, R, M, G, H, I or Y;

wherein the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆ does not correspond to an amino acid sequence of the Loop 1B region from the Class II solanaceous defensin prior to modification. 5. The artificially created defensin of Aspect 4 wherein the Loop 1B comprises the sequence X₁ X₂ X₃ X₄ X₅ X₆, SEQ ID NO:55, wherein:

X₁ is N, H, Q, D, K or E;

X₂ is R, H, T, K or G;

X₃ is F, H, Y or W;

X₄ is P, K, S or R;

X₅ is G or F; and/or

X₆ is P, V, I or N.

6. The artificially created defensin of Aspect 3 wherein:

X₁ is an amino acid selected from the list consisting of: L, F, S, I, A, H, Y, Q, D, K, G;

X₂ is an amino acid selected from the list consisting of: S, V, F, I, K, L, A, P, N, T, R, H, G;

X₃ is an amino acid selected from the list consisting of: A, F, W, N, I, S, Y, P, L, H;

X₄ is an amino acid selected from the list consisting of: K, G, E, R, A, P, F, Q, V, S;

X₅ is an amino acid selected from the list consisting of: M, G, K, D, S, Y, P, E, N, F; and

X₆ is an amino acid selected from the list consisting of: V, T, M, S, W, A, P, G, E, K, L, H, I, N. See SEQ ID NO:56.

7. The artificially created defensin of Aspects 3 or 4 or 5 or 6 wherein the Loop 1B on the Class II solanaceous defensin is modified to the amino acid sequence HRFKGP (SEQ ID NO:29) (NaD2), QHHSFP (SEQ ID NO:30) (Zea2), DTYRGV (SEQ ID NO:31) (PsD1), DKYRGP (SEQ ID NO:33) (MsDef1), KTFKGI (SEQ ID NO:34) (SoD2), KTWSGN (SEQ ID NO:35) and (DmAMP1) or a Loop 1B defined by SEQ ID NO:67 to SEQ ID NO:79. 8. The artificially created defensin of any one of Aspects 1 to 7 wherein the Class II solanaceous defensin comprises a C-terminal end region of a mature domain having at least 70% similarity to SEQ ID NO:52 after optimal alignment. 9. The artificially created defensin of Aspect 8 wherein the Class II solanaceous defensin is selected from NaD1, NsD1, NsD2, PhD1, PhD2, TPP3, FST, NeThio1, NeThio2, NpThio1, Na-gth, Cc-gth, C20 or SL549. 10. The artificially created defensin of Aspect 9 wherein the Class II solanaceous defensin is NaD1. 11. The artificially created defensin of Aspect 9 wherein the Class II solanaceous defensin is a defensin from Nicotiana suaveolens selected from NsD1 and NsD2. 12. The artificially created defensin of Aspect 2 wherein a Loop 1B from a non-Class II solanaceous defensin listed in FIG. 2 replaces the Loop 1B on the Class II solanaceous defensin. 13. The artificially created defensin of Aspect 7 wherein the Loop 1B is a modified form of NTFPGI from NaD1 (amino acids 8-13 of SEQ ID NO:2) wherein the modification comprises one or more of:

the N is substituted with an amino acid residue selected from A, R, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof;

the T is substituted with an amino acid residue selected from A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, W, Y or V or a naturally occurring modified form thereof;

the F is substituted with an amino acid residue selected from A, R, N, D, C, Q, E, G, H, I, L, K, M, P, S, T, W, Y or V or a naturally occurring modified form thereof;

the P is substituted with an amino acid residue selected from A, R, N, D, C, Q, E, G, H, I, L, K, M, F, S, T, W, Y or V or a naturally occurring modified form thereof;

the G is substituted with an amino acid residue selected from A, R, N, D, C, Q, E, H, I, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof; and/or

the I is substituted by an amino acid residue selected from A, R, N, D, C, Q, E, G, H, L, K, M, F, P, S, T, W, Y or V or a naturally occurring modified form thereof;

wherein the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆ does not correspond to an amino acid sequence of the Loop 1B region from the Class II solanaceous defensin prior to modification. 14. The artificially created defensin of Aspect 13 wherein Loop 1B is a modified form of NTFPGI from NaD1 (amino acids 8-13 of SEQ ID NO:2) wherein the modification comprises one or more of:

the N is substituted with an amino acid residue selected from G, D, H, K, A, E, Q, T, P, L, M, S and R;

the T is substituted with an amino acid residue selected from K, R, G, H, L, N, F, I, S and Y;

the F is substituted with an amino acid residue selected from W, Y, H, L, G and P;

the P is substituted with an amino acid residue selected from K, S, R, H, T, E, V, N, Q, D or G;

the G is substituted with an amino acid residue selected from S, K, Y, F and H; and/or

the I is substituted by an amino acid residue selected from P, V, L, T, A, F, N, K, R, M, G, H and Y; See also SEQ ID NO:87.

wherein the amino acid sequence X₁ X₂ X₃ X₄ X₅ X₆ does not correspond to an amino acid sequence of the Loop 1B region from the Class II solanaceous defensin prior to modification. 15. The artificially created defensin of any one of Aspects 1 to 14 wherein the backbone Class II solanaceous defensin further comprises an amino acid substitution, addition and/or deletion on the backbone outside said loop region. 16. The artificially created defensin of Aspect 15 wherein the further amino acid substitution, addition and/or deletion is a substitution of one or more amino acids in the C-terminal tail. 17. The artificially created defensin of any one of Aspects 1 to 16 wherein having the enhanced anti-pathogen activity selected from a broader spectrum of anti-pathogen activity, increased anti-pathogen activity, greater stability and/or greater permeabilization ability relative to the backbone Class II solanaceous defensin. 18. The artificially created defensin of Aspect 17 wherein the anti-pathogen activity is the level of activity against a fungus. 19. The artificially created defensin of Aspect 17 wherein the anti-pathogen activity is the level of activity against an insect. 20. The artificially created defensin of Aspect 18 wherein the fungus is a plant fungal pathogen. 21. The artificially created defensin of Aspect 20 wherein the fungus is a mammalian fungal pathogen. 22. The artificially created defensin of Aspect 21 wherein the fungus is a human fungal pathogen. 23. The artificially created defensin of Aspect 20 wherein the fungus is selected from Colletotrichum graminicola, Diplodia maydis, Fusarium graminearum and Fusarium verticilloides. 24. The artificially created defensin of Aspect 20 wherein the fungus is selected from Corn: Gibberella zeae (Fusarium graminearum), Colletotrichum graminicola, Stenocarpella maydi (Diplodia maydis), Fusarium moniliforme var. subglutinans, Fusarium verticilloides, Bipolaris maydis O, T (Cochliobolis heterostrophus), Exserohilum turcicum I, II and III, Cercospora zeae-maydis, Pythium irregulare, Pythium debaryanum, Pythium graminicola, Pythium splendens, Pythium ultimum, Pythium aphanidermatum, Aspergillus spp, Aspergillus flavus, Helminthosporium carbonum I, II and III (Cochliobolus carbonum), Helminthosporium pedicellatum, Physoderma maydis, Phyllosticta maydis, Kabatiella maydis, Cercospora sorghi, Ustilago maydis, Ustilago zeae, Puccinia sorghi, Puccinia polysora, Macrophomina phaseolina, Penicillium oxalicum, Nigrospora oryzae, Cladosporium herbarium, Curvularia lunata, Curvularia inaequalis, Curvularia pallescens, Trichoderma viride, Claviceps sorghi, Diplodia macrospora, Sclerophthora macrospora, Peronosclerospora sorghi, Peronosclerospora philippinensis, Peronosclerospora maydis, Peronosclerospora sacchari, Sphacelotheca reiliana, Physopella zeae, Cephalosporum maydis, Cephalosporum acremonium; Soybeans: Fusarium virgululiforme, Fusarium solani, Sclerotinia sclerotiorum, Fusarium oxysporum, Fusarium tucumaniae, Phakopsora pachyrhizi, Phytophthora megasperma f. sp. glycinea, Phytophthora sojae, Macrophomina phaseolina, Rhizoctonia solani, Sclerotinia sclerotiorum Diaporthe phaseolorum var. sojae (Phomopsis sojae), Diaporthe phaseolorum var. caulivora, Sclerotium rolfsii, Cercospora kikuchii, Cercospora sojina, Peronospora manshurica, Colletotrichum dematium (Colletotrichum truncatum), Corynespora cassiicola, Septoria glycines, Phyllosticta sojicola, Alternaria alternata, Microsphaera diffusa, Fusarium semitectum, Phialophora gregata, Glomerella glycines, Pythium aphanidermatum, Pythium ultimum, Pythium debaryanum; Canola: Albugo candida, Alternaria brassicae, Leptosphaeria maculans, Rhizoctonia solani, Sclerotinia sclerotiorum, Mycosphaerella brassicicola, Pythium ultimum, Peronospora parasitica, Fusarium oxysporum, Fusarium avenaceum, Fusarium roseum, Alternaria alternata; Cotton: Fusarium oxysporum f. sp. vasinfectum, Verticillium dahliae, Thielaviopsis basicola, Alternaria macrospora, Cercospora gossypina, Phoma exigua (Ascochyta gossypii), Pythium spp Rhizoctonia solani, Puccinia scheddardii, Puccinia cacabata, Phymatotrichopsis omnivore; Canola: Leptosphaeria maculans, Sclerotinia sclerotiorum, Alternaria brassicae, Alternaria brasicicola, Plasmodiophora brassicae, Rhizoctonia solani, Fusarium spp, Pythium spp, Phytophthora spp, Alternaria spp, Peronospora parasitica, Mycosphaerella capsellae (Pseudocercosporella capsellae), Albugo candida, Phytophtohora megasperma var. megasperma, Botrytis cinerea, Erysiphe cruciferarum; Wheat: Cochliobolus sativus, Drechslera wirreganensis, Mycosphaerella graminicola, Phaeosphaeria avenaria f. sp. triticea, Phaeosphaeria nodorum, Blumeria graminis f. sp. tritici, Urocystis agropyri, Alternaria alternata, Cladosporium herbarum, Fusarium graminearum, Fusarium avenaceum, Fusarium culmorum, Fusarium pseudograminearum, Ustilago tritici, Ascochyta tritici, Cephalosporium gramineum, Colletotrichum graminicola, Erysiphe graminis f. sp. tritici, Puccinia graminis f. sp. tritici, Puccinia recondita f. sp. tritici, Puccinia striiformis, Puccinia triticina, Sclerophthora macrospora, Urocystis agropyri, Pyrenophora tritici-repentis, Pyrenophora semeniperda, Phaeosphaeria nodorum, Septoria nodorum, Septoria tritici, Septoria avenae, Pseudocercosporella herpotrichoides, Rhizoctonia solani, Rhizoctonia cerealis, Gaeumannomyces graminis var. tritici, Pythium spp, Pythium aphanidermatum, Pythium arrhenomannes, Pythium gramicola, Pythium ultimum, Bipolaris sorokiniana, Claviceps purpurea, Tapesia yallundae, Tilletia tritici, Tilletia laevis, Tilletia caries, Tilletia indica, Ustilago tritici, Wojnowicia graminis, Cochliobolus sativus; Sorghum: Exserohilum turcicum, Colletotrichum sublineolum, Cercospora sorghi, Gloeocercospora sorghi, Ascochyta sorghina, Puccinia purpurea, Macrophomina phaseolina, Perconia circinata, Fusarium moniliforme, Alternaria alternata, Bipolaris sorghicola, Helminthosporium sorghicola, Curvularia lunata, Phoma insidiosa, Ramulispora sorghi, Ramulispora sorghicola, Phyllachara saccari, Sporisorium reilianum (Sphacelotheca reiliana), Sphacelotheca cruenta, Sporisorium sorghi, Claviceps sorghi, Rhizoctonia solani, Acremonium strictum, Sclerophthona macrospora, Peronosclerospora sorghi, Peronosclerospora philippinensis, Sclerospora graminicola, Fusarium graminearum, Fusarium oxysporum, Pythium arrhenomanes, Pythium graminicola; Sunflower: Plasmopara halstedii, Sclerotinia sclerotiorum, Septoria helianthi, Phomopsis helianthi, Alternaria helianthi, Alternaria zinniae, Botrytis cinerea, Phoma macdonaldii, Macrophomina phaseolina, Erysiphe cichoracearum, Rhizopus oryzae, Rhizopus arrhizus, Rhizopus stolonifer, Puccinia helianthe, Verticillium dahliae, Cephalosporum acremonium, Phytophthora cryptogea, Albugo tragopogonis; Alfalfa: Pythium ultimum, Pythium irregulare, Pythium splendens, Pythium debaryanum, Pythium aphanidermatum, Phytophthora megasperma, Peronospora trifollorum, Phoma medicaginis var. medicaginis, Cercospora medicaginis, Pseudopeziza medicaginis, Leptotrochila medicaginis, Fusarium oxysporum, Verticillium albo-atrum, Aphanomyces euteiches, Stemphylium herbarum, Stemphylium alfalfae, Colletotrichum trifolii, Leptosphaerulina briosiana, Uromyces striatus, Sclerotinia trifoliorum, Stagonospora meliloti, Stemphylium botryosum and Leptotrichila medicaginis. 25. The artificially created defensin of Aspect 24 wherein the fungus is selected from Fusarium graminearum, Colletotrichum graminicola, Stenocarpella maydis, Fusarium verticilloides, Cochliobolis heterostrophus, Exserohilum turcicum, Cercospora zea-maydis, Fusarium virguhforme, Fusarium solanai, Sclerotinia sclerotiorum, Fusarium oxysporum, Fusarium tucumaniae, Phakopsora pachyrhizi. 26. The artificially created defensin of Aspect 24 wherein the fungus is selected from Fusarium virguluhforme, Fusarium solani, Sclerotinia sclerotiorum, Fusarium oxysporum, Fusarium tucumaniae. 27. The artificially created defensin of Aspect 20 wherein the fungus is a rust. 28. The artificially created defensin of Aspect 21 wherein the fungus is selected from Alternaeria spp, Aspergillus spp, Candida spp, Fusarium spp, Trychophyton spp, Cryptococcus spp, Microsporum spp, Penicillium spp, Trichosporon spp, Scedosporium spp, Paeciliomyces spp, Acremonium spp and Dermatiaceous molds. 29. The artificially created defensin of Aspect 24 wherein the fungus is selected from Alternaria alternata, Aspergillus fumigatus, Aspergillus niger, Aspergillus flavus, Aspergillus nidulans, Aspergillus paraciticus, Candida albicans, Candida dubliniensis, Candida famata, Candida glabrata, Candida guilliermondii, Candida haemulonii, Candida kefyr, Candida krusei, Candida lusitaniae, Candida norvegensis, Candida parapsilosis, Candida tropicalis, Candida viswanathii, Fusarium oxysporum, Fusarium solani, Fusarium monoliforme, Trycophyton rubrum, Trycophyton mentagrophytes, Trycophyton interdigitales, Trycophyton tonsurans, Cryptococcus neoformans, Cryptococcus gattii, Cryptococcus grubii, Microsporum canis, Microsporum gypseum, Penicillium mameffei, Tricosporon beigelii, Trichosporon asahii, Trichosporon inkin, Trichosporon asteroides, Trichosporon cutaneum, Trichosporon domesticum, Trichosporon mucoides, Trichosporon ovoides, Trichosporon pullulans, Trichosporon loubieri, Trichosporon japonicum, Scedosporium apiospermum, Scedosporium prolificans, Paecilomyces variotii, Paecilomyces lilacinus, Acremonium stricutm, Cladophialophora bantiana, Wangiella dermatitidis, Ramichloridium obovoideum, Chaetomium atrobrunneum, Dactlaria gallopavum, Bipolaris spp, Exserohilum rostratum as well as Absidia corymbifera, Apophysomyces elegans, Mucor indicus, Rhizomucor pusillus, Rhizopus oryzae, Cunninghamella bertholletiae, Cokeromyces recurvatus, Saksenaea vasiformis, Syncephalastrum racemosum, Basidiobolus ranarum, Conidiobolus coronatus/Conidiobolus incongruus, Blastomyces dermatitidis, Coccidioides immitis, Coccidioides posadasii, Histoplasma capsulatum, Paracoccidioides brasiliensis, Pseudallescheria boydii and Sporothrix schenckii. 30. The artificially created defensin of Aspect 19 wherein the insects are selected from Diatraea grandiosella, Ostrinia nubialis, Rhopalosiphum spp, Helicoverpa spp, Plutella xylostella and Lygus spp. 31. A composition comprising the artificially created defensin of any one of Aspects 1 to 30 and optionally further comprising a chemical or proteinaceous pathogenicide and/or a serine or cysteine proteinase inhibitor or a precursor form thereof. 32. An isolated nucleic acid molecule encoding an artificially created defensin of any one of Aspects 1 to 30. 33. A genetic construct comprising the isolated nucleic acid molecule of Aspect 32. 34. A genetically modified plant which produces an artificially created defensin of any one of Aspects 1 to 30 or progeny of said plant. 35. The genetically modified plant of Aspect 34 comprising a nucleic acid molecule of Aspect 32 or a genetic construct of Aspect 33 or its progeny or propagating material. 36. The genetically modified plant of Aspect 34 or 35 selected from corn, soybean, cotton, sorghum, wheat, barley, maize, canola, abaca, alfalfa, almond, apple, asparagus, banana, bean-phaseolus, blackberry, broad bean, cashew, cassava, chick pea, citrus, coconut, coffee, fig, flax, grapes, groundnut, hemp, lavender, mushroom, olive, onion, pea, peanut, pear, pearl millet, potato, rapeseed, ryegrass, strawberry, sugar beet, sugarcane, sunflower, sweetpotato, taro, tea, tobacco, tomato, triticale, truffle and yam. 37. A method for generating a genetically modified plant or its progeny which exhibit enhanced anti-pathogen activity, the method comprising creating a plant which comprises cells which express the nucleic acid encoding a modified Class II solanaceous defensin of any one of Aspects 1 to 30, the level of expression in the plant or its progeny sufficient for the modified defensin to exhibit a protective effect against plant pathogens. 38. A method of controlling pathogen infestation on a plant, the method comprising topically applying a composition of Aspect 31 to the plant, its roots or soil surrounding the plant. 39. A method of controlling pathogen infestation on an animal subject, the method comprising topically applying a composition of Aspect 31 to a surface on the animal potentially infested by the pathogen. 40. The method of Aspect 37 or 38 further applying a chemical pathogenicide, a proteinaceous pathogenicide or a serine or cysteine proteinase inhibitor or a precursor form thereof. 41. The method of Aspect 39 wherein the animal is a mammal. 42. The method of Aspect 31 wherein the mammal is a human. 43. Use of an artificially created defensin comprising a backbone amino acid sequence from a Class II solanaceous defensin having a loop region between β-strand 1 and the α-helix on the N-terminal end portion of the Class II solanaceous defensin wherein the loop region is modified by a single or multiple amino acid substitution, deletion and/or addition in the manufacture of an anti-pathogen medicament. 44. Use of Aspect 43 wherein the loop region is Loop 1B. 45. Use of Aspect 43 or 44 wherein the pathogen is a fungus. 46. Use of Aspect 43 or 44 or 45 further comprising use of a chemical pathogenicide, a proteinaceous pathogenicide or a serine or cysteine proteinase inhibitor or a precursor form thereof. 47. An isolated defensin from Nicotiana suaveolens having an amino acid sequence as set forth in SEQ ID NO:49 [NsD1] or an amino acid sequence having at least 70% thereto after optimal alignment. 48. An isolated defensin from Nicotiana suaveolens having an amino acid sequence as set forth in SEQ ID NO:51 [NsD2] or an amino acid sequence having at least 70% thereto after optimal alignment. 49. An isolated nucleic acid molecule or comprising a sequence of nucleotides encoding the defensin of Aspect 47 or 48. 50. The isolated nucleic acid molecule of Aspect 49 comprising a nucleotide sequence selected from SEQ ID NO:48, SEQ ID NO:50, a nucleotide sequence capable of hybridizing to SEQ ID NO:48 or 50, under medium stringency conditions and a nucleotide sequence having at least 70% identity to SEQ ID NO:46 or 48 after optimal alignment. 51. Use of a Class II solanaceous defensin comprising a C-terminal end region of its mature domain having at least about 70% similarity to SEQ ID NO:52 in the manufacture of an artificially created defensin comprising a modified Loop 1B region and which artificially created defensin exhibits anti-pathogen activity. 52. A genetic construct comprising a nucleic acid of Aspect 32 and a nucleic acid encoding a proteinase inhibitor.

EXAMPLES

Aspects are further described by the following non-limiting Examples. Methods used in these Examples are described below.

Purification of Defensins from Solanaceous Flowers

To isolate class II defensins from their natural source, whole N. alata (NaD1, NaD2) or N. suaveolens (NsD1, NsD2) flowers up to the petal coloration stage of flower development were ground to a fine powder and extracted in dilute sulfuric acid as previously described previously (Lay et al. 2003 supra). Briefly, flowers (760 g wet weight) were frozen in liquid nitrogen, ground to a fine powder in a mortar and pestle, and homogenized in 50 mM sulfuric acid (3 mL per g fresh weight) for 5 min using an Ultra-Turrax homogenizer. After stirring for 1 h at 4° C., cellular debris was removed by filtration through Miracloth (Calbiochem, San Diego, Calif.) and centrifugation (25,000×g, 15 min, 4° C.). The pH was then adjusted to 7.0 by addition of 10 M NaOH and the extract was stirred for 1 h at 4° C. before centrifugation (25,000×g, 15 min, 4° C.) to remove precipitated proteins. The supernatant (1.8 L) was applied to an SP Sepharose (Trademark) Fast Flow (GE Healthcare Bio-Sciences) column (2.5×2.5 cm) pre-equilibrated with 10 mM sodium phosphate buffer. Unbound proteins were removed by washing with 20 column volumes of 10 mM sodium phosphate buffer (pH 6.0) and bound proteins were eluted in 3×10 mL fractions with 10 mM sodium phosphate buffer (pH 6.0) containing 500 mM NaCl. Fractions from the SP Sepharose column were subjected to reverse-phase high performance liquid chromatography (RP-HPLC).

Purification of NaD1 from Pichia pastoris

The Pichia pastoris expression system is well-known and commercially available from Invitrogen (Carlsbad, Calif.; see the supplier's Pichia Expression Manual disclosing the sequence of the pPIC9 expression vector).

A single pPIC9-NaD1 P pastoris GS115 colony was used to inoculate 10 mL of BMG medium (described in the Invitrogen Pichia Expression Manual) in a 100 mL flask and was incubated overnight in a 30° C. shaking incubator (140 rpm). The culture was used to inoculate 500 mL of BMG in a 2 L baffled flask which was placed in a 30° C. shaking incubator (140 rpm). Once the OD600 reached 2.0 (˜18 h), cells were harvested by centrifugation (2,500×g, 10 min) and resuspended into 1 L of BMM medium (OD600=1.0) in a 5 L baffled flask and incubated in a 28° C. shaking incubator for 3 days. The expression medium was separated from cells by centrifugation (4750 rpm, 20 min) and diluted with an equal volume of 20 mM potassium phosphate buffer (pH 6.0). The medium was adjusted to pH 6.0 with NaOH before it was applied to an SP Sepharose column (1 cm×1 cm, Amersham Biosciences) pre-equilibrated with 10 mM potassium phosphate buffer, pH 6.0. The column was then washed with 100 mL of 10 mM potassium phosphate buffer, pH 6.0 and bound protein was eluted in 10 mL of 10 mM potassium phosphate buffer containing 500 mM NaCl. Eluted proteins were subjected to RP-HPLC using a 40 minute linear gradient as described herein below. Protein peaks were collected and analyzed by SDS-PAGE and immunoblotting with the anti-NaD1 antibody. Fractions containing NaD1 were lyophilized and resuspended in sterile milli Q ultrapure water. The protein concentration of Pichia-expressed NaD1 was determined using the bicinchoninic acid (BCA) protein assay (Pierce Chemical Co.) with bovine serum albumin (BSA) as the protein standard.

Reverse-Phase High Performance Liquid Chromatography

Reverse-phase high performance liquid chromatography (RP-HPLC) was performed on a System Gold HPLC (Beckman) coupled to a detector (model 166, Beckman) using a preparative C8 column (22×250 mm, Vydac) with a guard column attached. Protein samples were loaded in buffer A (0.1% [v/v] trifluoroacetic acid) and eluted with a linear gradient of 0-100% [v/v] buffer B (60% [v/v] acetonitrile in 0.089% [v/v] trifluoroacetic acid) at a flow rate of 10 mL/min over 40 min. Proteins were detected by monitoring absorbance at 215 nm. Protein peaks were collected and analyzed by SDS-PAGE.

Samples from each stage of NaD1 purifications (30 μL) were added to NuPAGE (Registered Trademark) LDS sample loading buffer (10 μL, Invitrogen) and heated to 70° C. for 10 min. The samples were then loaded onto NuPAGE (Registered Trademark) precast 4-12% [w/v] Bis-Tris polyacrylamide gels (Invitrogen) and the proteins were separated using an XCell-Surelock electrophoresis apparatus (Invitrogen) run at 200 V. Proteins were visualized by Coomassie Blue staining or transferred onto nitrocellulose for immunoblotting with the anti-NaD1 antibodies.

Circular Dichroism Spectrum of rNaD1

To examine whether NaD1 purified from P. pastoris (rNaD1) was correctly folded, its far UV circular dichroism (CD) spectrum was recorded and compared with that of native NaD1. The similarity of the two spectra indicates the structure of rNaD1 was not significantly altered compared to native NaD1.

PCR Mutagenesis of NaD1

Site directed mutagenesis of NaD1 was carried out using the Phusion (Registered Trademark) site-directed mutagenesis kit (Finnzymes). Oligonucleotide primers phosphorylated at the 5′ end were designed to incorporate the desired mutation. The entire template plasmid (pPIC9-NaD1) was amplified in a PCR reaction of 30 cycles with the following temperature profile; 98° C., 30 s; 55° C., 20 s; 72° C., 4 min with a final extension cycle of 72° C. for 10 min. The linear PCR product was then circularized using T4 DNA Quick Ligase for 5 min at RT and transformed into chemically competent TOP10 cells according to the manufacturer's instructions. Constructs were sequenced using the AOX3′ primer to ensure the mutation had been correctly incorporated.

Preparation of Electrocompetent P. pastoris

Electrocompetent P. pastoris GS115 cells (Invitrogen) were prepared as described by Chang et al. (2005) Mol Biol Cell 16(10):4941-4953. Briefly, cells grown overnight in YPD (1% w/v Bacto yeast extract, 2% w/v Bacto peptone extract, and 2% w/v dextrose) were harvested and treated with YPD containing 10 mM DTT, 25 mM HEPES, pH 8, for 15 min at 30° C. with shaking. Cells were washed twice in water and once in ice-cold 1 M sorbitol, before they were resuspended in 1 M sorbitol and divided into 80 μL aliquots for storage at −80° C.

Transformation of P. pastoris GS115 with pPIC9 Constructs

Single E. coli TOP10 colonies transformed with each pPIC9 construct were used to inoculate 10 mL of LB containing 100 μg/mL ampicillin and incubated overnight at 37° C. in a shaking incubator. Plasmid DNA was isolated using the Qiaprep (Registered Trademark) miniprep kit (Qiagen) and linearized overnight using the restriction enzyme SalI. Competent P. pastoris GS115 cells (80 μL) were thawed on ice and 1 μg of linearized DNA was added in an ice-cold Gene Pulser (Registered Trademark) electroporation cuvette with a 0.2 cm gap. DNA was introduced by electroporation at 1.5 kV, 25 μF, 400Ω (Gene Pulser, Bio-Rad Laboratories). Ice-cold 1 M sorbitol (1 mL) was added to the cells before they were plated onto MD plates (1.34% w/v yeast nitrogen base, without amino acids and with ammonium sulfate [US Biological, YNB], 4×10⁻⁵% w/v biotin, 2% w/v dextrose) and incubated at 30° C. for 5 days. Positive colonies were then selected and re-plated onto fresh MD plates.

Characterization of rNaD1

FIGS. 6A through D show an immunoblot, reverse phase HPLC trace, structure of rNaD1 isolated from flowers and activity of rNaD1 against hyphal growth.

Amino Acid Sequence Comparisons

FIGS. 3A and 3B provide a representation of amino acid sequences of various Class II solanaceous defensins including NaD1. FIG. 4 shows Class I and II defensins. The Loop 1B region in these alignments comprises amino acids 10 through 15 in FIG. 3 and amino acids 9 through 14 in FIG. 4. The present disclosure extends to a defensin having the C-terminal 20 contiguous amino acid residues with at least 70% similarity to amino acids 32 to 51 (FIG. 3) of NaD1 (SEQ ID NO:52). Examples are provided in Table 4.

Vector Maps

FIG. 11 shows a vector map for pHEX138.

Bioassay Method for in Planta Studies:

Preparation of C. graminicola Inoculum:

Colletotrichum graminicola (US isolate Carroll-1A-99) was isolated from Zea maize (Pioneer Hi-Bred International, Inc. Johnston, Iowa, USA). Spores were isolated from sporulating cultures grown on V8 agar for approximately 2-3 Weeks. C. graminicola spores were collected by scraping the surface of the plates in sterile water and separating spores from hyphal matter by filtration through facial tissue. The concentration of spores in the filtrate was measured using a haemocytometer.

Preparation of F. graminearum Inoculum:

Fusarium graminearum isolate (73B1A) was isolated from Zea maize (Pioneer Hi-Bred International, Inc. Johnston, Iowa, USA). Spores were isolated from sporulating cultures grown on SNP agar for approximately 2-3 Weeks. F. graminearum spores were collected by scraping the surface of the plates in sterile water. The concentration of spores in was measured using a haemocytometer.

Inoculation of Maize Plants:

Plants for bioassay were grown in the glasshouse for approximately 9-10 weeks after deflasking.

C. gramincola Inoculation

Two wounds, 2.0 mm in length were made on opposing sides of the maize leaf sheath and then over laid with 1×10⁶ C. graminicola spores/mL. Wounds were then sealed with Glad Pressn'Seal for three days. The area of infection was measured by digital photography 10 days post inoculation.

F. graminearum Inoculation

Two wounds, 2.0 mm in length were made on opposing sides of the maize leaf sheath. Wounds were over laid 6 mm diameter paper discs dipped in 1×10⁶ F. graminearum spores/mL. Wounds were then sealed with Glad Pressn'Seal for three days. The area of infection was measured by digital photography 10 days post inoculation.

ELISA Method

Protein extract: leaf sheaths were excised from plants grown in the glasshouse. The tissue (50 mg) was frozen in liquid nitrogen and ground in a mixer mill (Retsch MM300) for 2×15 sec at frequency 30 s⁻¹. Protein extracts were made by adding 450 μL 2% insoluble PVPP (Polyclar)/PBS/0.05% Tween 20 and vortexing for 20 s. The samples were centrifuged for 10 min and the supernatant was collected.

ELISA plates (Nunc Maxisorp #442404) were incubated with 100 μL/well of primary antibody in PBS (100 ng/well of anti-NaD1 (polyclonal antibody was made by a standard method to purified NaD1 from flowers of Nicotiana alata)). Plates were incubated overnight at 4° C. in a humid box. They were then washed for 2 min×4 with PBS/0.05% v/v Tween 20. Plates were blocked with 200 μL/well 3% w/v BSA (Sigma A-7030: 98% ELISA grade) in PBS and incubated for 2 h at 25° C. Plates were then washed for 2 min×4 with PBS/0.05% v/v Tween 20.

Corn sheath protein extracts (100 μL/well diluted in PBS/0.05% v/v Tween 20) were then applied to the plates which were then incubated for 2 h at 25° C. Plates were then washed for 2 min×4 with PBS/0.05% v/v Tween 20 and then 100 μL/well of secondary antibody in PBS (75 ng/well biotin-labelled NaD1 antibody) was applied. The biotin labelled antibody was prepared using the EZ-link Sulfo-NHS-LC-biotinylation kit (Pierce); 2 mL of protein A purified antibody and 2 mg of the biotin reagent were used. Plates were incubated for 1 h at 25° C. and then washed for 2 min×4 with PBS/0.05% v/v Tween 20 and 100 μL/well of NeutriAvidin HRP-conjugate (Pierce #31001; 1:1000 dilution; 0.1 μL/well) in PBS was applied. The plates were incubated for 1 h at 25° C. and then washed for 2 min×2 with PBS/0.05% v/v Tween 20, followed by 2 min×2 with H₂O. Just before use, substrate was prepared by dissolving 1 ImmunoPure OPD tablet (Pierce #34006) in 9 mL H₂O, then adding 1 mL stable peroxide buffer (10×, Pierce #34062). The substrate was applied at 100 μL/well and plates were incubated at 25° C. until color developed. The reaction was stopped by applying 50 μL 2.5 M sulfuric acid. Absorbance at 490 nm was measured in a plate reader (Molecular Devices).

Immunoblot Analysis

Leaf sheaths were excised from plants grown in the glasshouse. Leaf sheath tissue (50 mg) was frozen in liquid nitrogen and ground to a fine powder in a mixer mill (Retsch MM300) for 2×15 s at frequency 30 s⁻¹. Samples were extracted by adding 2% w/v insoluble PVPP (Polyclar)/PBS/0.05% v/v Tween 20 (75 μL) and vortexing. Samples were then centrifuged at 14,000 rpm for 10 min and the supernatants retained. To the supernatant (21 μL), Novex NuPAGE 4×LDS sample buffer (7.5 μL) and β-mercaptoethanol (1.5 μL) were added and heated at 70° C. for 10 min.

Extracted leaf sheath proteins were separated by SDS-PAGE on preformed 4-12% w/v polyacrylamide gradient gels (Novex, NuPAGE bis-tris, MES buffer) for 35 min at 200V in a Novex X Cell Il mini-cell electrophoresis apparatus. Prestained molecular weight markers (Novex SeeBlue Plus 2) were included as a standard. Proteins were transferred to nitrocellulose membrane (Osmonics 0.22 micron NitroBind) for 60 min at 30 V using the Novex X Cell mini-cell electrophoresis apparatus in NuPAGE transfer buffer with 10% v/v methanol. After transfer, membranes were incubated for 1 min in isopropanol, followed by a 5 min wash in TBS.

The membrane was blocked for 1 h in 3% w/v BSA at room temperature followed by incubation with primary antibody overnight at room temperature (mature NaD1 or HvCPI6 antibody diluted 1 in 1000 in TBS/1% w/v BSA of 1 mg/ml stock). The membrane was washed 5×10 min in TBST before incubation with goat anti-rabbit IgG conjugated to horseradish peroxidase for 60 min at RT (Pierce, 1 in 50,000 dilution in TBS). Five further 10 min TBST washes were performed before the membrane was incubated with SuperSignal West Pico Chemiluminescent substrate (Pierce) according to the manufacturer's instructions. Membranes were exposed to ECL Hyperfilm (Amersham).

TABLE 4 Seq−> NaD1. NsD1. NsD2. PhD1. PhD2. TPP3. FST. NeThio1. NaD1. ID 100%  95% 90% 100%  80% 95% 100%  NsD1. 100%  ID 95% 90% 100%  80% 95% 100%  NsD2. 95% 95% ID 90% 95% 75% 90% 95% PhD1. 90% 90% 90% ID 90% 70% 85% 90% PhD2. 100%  100%  95% 90% ID 80% 95% 100%  TPP3. 80% 80% 75% 70% 80% ID 85% 80% FST. 95% 95% 90% 85% 95% 85% ID 95% NeThio1. 100%  100%  95% 90% 100%  80% 95% ID NeThio2. 100%  100%  95% 90% 100%  80% 95% 100%  Na-gth. 85% 85% 80% 75% 85% 65% 80% 85% NpThio1. 85% 85% 80% 75% 85% 65% 80% 85% Cc gth. 75% 75% 75% 75% 75% 85% 80% 75% Accession Seq−> NeThio2. Na-gth. NpThio1. Cc gth. Source number NaD1. 100%  85% 85% 75% Nicotiana Q8GTM0 alata NsD1. 100%  85% 85% 75% Nicotiana none suaveolens NsD2. 95% 80% 80% 75% Nicotiana none suaveolens PhD1. 90% 75% 75% 75% Petunia Q8H6Q1 hybrida PhD2. 100%  85% 85% 75% Petunia Q8H6Q0 hybrida TPP3. 80% 65% 65% 85% Solanum AAA80496 lycopersicum FST. 95% 80% 80% 80% Nicotiana P32026 tabacum NeThio1. 100%  85% 85% 75% Nicotiana BAA21114 excelsior NeThio2. ID 85% 85% 75% Nicotiana BAA21113 excelsior Na-gth. 85% ID 100%  60% Nicotiana AAS13436 attenuata NpThio1. 85% 100%  ID 60% Nicotiana O24115 paniculata Cc gth. 75% 60% 60% ID Capsicum AAD21200 chinense

Example 1 Antifungal Activity of Class I Defensins

Three Class I defensins were either purified from their native source (NaD2) or expressed using P. pastoris expression system (γ-zeathionin2, γ-hordothionin) as described in the methods. The anti-fungal activity of the peptides was assessed against Fusarium graminearum essentially as described in Broekaert et al. (1990) FEMS Microbiol Lett 69:55-60, 1990, and compared to that of two solanaceous class II defensins (NaD1, NsD1). Spores were isolated from sporulating cultures growing in half-strength potato dextrose broth (PDB) by filtration through sterile muslin. Spore concentrations were determined using a hemocytometer and adjusted to 5×10⁴ spores/mL in ½×PDB. Spore suspensions (80 μL) were added to the wells of sterile 96-well flat-bottomed microtitre plates along with 20 μL of filter-sterilized (0.22 μm syringe filter; Millipore) protein, or water to give final protein concentrations of 0-10 μM. The plates were shaken briefly and placed in the dark at 25° C. without shaking for 28 h. Hyphal growth was estimated by measuring the optical density at 595 nm using a microtitre plate reader (SpectraMax Pro M5e; Molecular Devices). Each test was performed in triplicate. Results (FIG. 7) showed that the Class I defensins tested exhibited low antifungal activity.

Example 2 Modification to NaD1 Loop 1B Region on a Class II Solanaceous Defensin

The first aspect of this example is the selection of a Class II solanaceous defensin. Defensins are screened to identify defensins having a C-terminal portion comprising an amino acid sequence as set forth in SEQ ID NO:52 or having at least 70% similarity thereto after optimal alignment (Table 4). FIG. 3 shows the type of alignment. SEQ ID NO:50 represents the terminal 20 continguous amino acids including the most C-terminal invariant cysteine residue. NaD1, NsD1 PhD2, NeThio1 and NeThio2 are examples of defensins having 100% similarity to SEQ ID NO:52.

NaD1 is selected as the Class II solanaecous defensin backbone. This defensin comprises a Loop 1B having the amino acid sequence: NTFPGI (SEQ ID NO:12).

One or more of the amino acid residues NTFPGI is/are substituted by another amino acid residue. All six residues may be altered or 1 or 2 or 3 or 4 or 5 of the residues may be changed. This includes a single amino acid substitution or a Loop 1B swap. Examples of changes made include the following sequences (together with the source in parantheses):

[SEQ ID NO: 29] HRFKGP (NaD2); [SEQ ID NO: 30] QHHSFP (Zea2); [SEQ ID NO: 31] DTYRGV (PsD1); [SEQ ID NO: 32] PTWEGI (PsD2); [SEQ ID NO: 33] DKYRGP (MsDeF1(; [SEQ ID NO: 34] KTFKGI (SoD2); [SEQ ID NO: 35] KTWSGN (DmAMP1); [SEQ ID NO: 36] EGWXGK (VrD1); [SEQ ID NO: 37] GTWSGV (RsAFP2); and [SEQ ID NO: 38] AGFKGP (g1-H).

Other examples include selecting an amino acid sequence selected from SEQ ID NO:67 to 79.

Example 3 Inhibition of the Growth of Fusarium graminearum in the Presence of Loop Variants of NaD1

Recombinant NaD1 and the loop variants HXP4, HXP34 and HXP35 were expressed in the P. pastoris expression system and purified as described in the methods. The anti-fungal activity of the peptides against Fusarium graminearum was assessed essentially as described in Broekaert et al. (1990) FEMS Microbiol Lett 69:55-60. Spores were isolated from sporulating cultures growing in half-strength potato dextrose broth (PDB) by filtration through sterile muslin. Spore concentrations were determined using a hemocytometer and adjusted to 5×10⁴ spores/mL in ½×PDB. Spore suspensions (80 μL) were added to the wells of sterile 96-well flat-bottomed microtitre plates along with 20 μL of filter-sterilized (0.22 μm syringe filter; Millipore) protein, or water to give final protein concentrations of 0-10 μM. The plates were shaken briefly and placed in the dark at 25° C. without shaking for 28 h. Hyphal growth was estimated by measuring the optical density at 595 nm using a microtitre plate reader (SpectraMax Pro M5e; Molecular Devices). Each test was performed in triplicate.

Results

FIG. 8 illustrates the relative anti-fungal activity of the loop variants HXP4, HXP34 and HXP35 compared to NaD1 against F. graminearum (Fgr). At 0.825 ppm, HXP4, HXP34 and HXP35 inhibited the growth of F. graminearum by 41.7, 14.6 or 34.5% more than NaD1 respectively. At 1.65 ppm, all three loop variants inhibited the growth of F. graminearum by ˜70% more than NaD1.

Example 4 Inhibition of the Growth of Fusarium Verticilloides in the Presence of Loop Variants of NaD1

Recombinant NaD1 and the loop variants HXP4, HXP34 and HXP35 were expressed in the P. pastoris expression system and purified as described in the methods. The anti-fungal activity of the peptides against Fusarium verticilloides was assessed as described in Example 1.

Results

FIG. 9 illustrates the relative anti-fungal activity of the loop variants HXP4, HXP34 and HXP35 compared to NaD1 against F. verticilloides (Fve). At 3.25 ppm, HXP4, HXP34 and HXP35 inhibited the growth of F. verticilloides by 40.9, 29.4 and 5.1% more than NaD1 respectively. At 6.5 ppm, all three loop variants inhibited the growth of F. verticilloides by at least 67% more than NaD1.

Example 5 Inhibition of the Growth of Colletotrichum graminicola in the Presence of Loop Variants of NaD1

Recombinant NaD1 and the loop variants HXP4, HXP34 and HXP35 were expressed in the P. pastoris expression system and purified as described in the methods. The anti-fungal activity of the peptides against Colletotrichum graminicola was assessed as described in Example 1.

Results

FIG. 10 illustrates the relative anti-fungal activity of the loop variants HXP4, HXP34 and HXP35 compared to NaD1 against C. graminicola (Cgr). At 13 ppm, HXP4, HXP34 and HXP35 inhibited the growth of C. graminicola by 61.3, 21.8 or 83.2% more than NaD1, respectively.

Example 6 Production of Transgenic Plants

Transgenic canola (Brassica napus, cv RI64) expressing HXP4 was produced by Agrobacterium tumefaciens mediated transformation. The DNA binary vector used for the transformation (pHEX138) is described in FIG. 11. The binary vector was transferred into Agrobacterium tumefaciens by electroporation and the presence of the plasmid confirmed by gel electrophoresis. Cultures of Agrobacterium were used to infect hypocotyl sections of canola. Transgenic shoots were selected on the antibiotic kanamycin at 25 mg/L. Transgenic plants expressing HXP4 were selected using ELISA to detect soluble proteins extracted from leaves.

From three transformation experiments (CAT93, CAT94 and CAT96) 7 plants (6 events) had detectable levels of HXP4 (Table 5). The level of HXP4 protein ranged from 0.3 to 2.1 ppm (ng HXP4/mg fresh weight of leaf tissue).

TABLE 5 Transgenic canola line Level of HXP4 (ppm) 93.1.2 2.1 93.1.3 2.0 93.15.3 1.9 96.7.2 1.8 96.17.1 0.3 96.72.1 1.9 94.11.1 1.6 Glasshouse Bioassays with Leptosphaeria maculans

The pathogen Leptosphaeria maculans is grown on 10% (v/v) V8 agar plates for 1-2 weeks at room temperature. Pycnidiospores are isolated by covering the plate with sterilized water (5 mL) and scraping the surface of the agar to dislodge the spores. Spores are separated from the hyphal matter by filtration through sterile tissues. The concentration of the spores in the filtrate is measured using a hemocytometer and the final concentration is adjusted to between 1×10⁶ to 1×10⁷ pycnidiospores/mL with water.

Seedlings are grown in the glasshouse in small planting trays at 22° C. Approximately ten days after sowing, the two cotyledons of each seedling are punctured twice with a 26 gauge needle (once in each of the 2 lobes) and the wounded area is inoculated with a droplet of spores (5 μL). Controls are inoculated with water. The plants are maintained under high humidity conditions for 3 days to facilitate spore germination.

Disease symptoms are assessed up to 20 days after inoculation. Lesion size is quantified using computer software analysis (ImageJ) of digital images in mm². The average lesion size is statistically analyzed using non-parametric methods.

Example 7 Production of Transgenic Corn Plants Expressing HXP4

Transgenic corn plants are produced by Agrobacterium-mediated transformation or particle bombardment using standard protocols such as those described in U.S. Pat. No. 5,981,840; U.S. Pat. No. 7,528,293; U.S. Pat. No. 7,589,176; U.S. Pat. No. 7,785,828; Frame et al. (2002) Plant Physiology 129:13-22. A binary vector containing GAT as the selectable marker, a ubiquitin promoter for constitutive expression and a codon optimised sequence encoding either HXP4 or NaD1 under the control of a constitutive ubiquitin promoter as well as a sequence encoding encoding GAT as a selectable marker was transferred into an Agrobacterium tumefaciens strain by electroporation. Immature corn embryos were infected via immersion in a suspension of Agrobacterium followed by a period of co-culture on a solid medium. The embryos were then optionally “rested” during which time they were incubated in the presence of at least one antibiotic which inhibits the growth of Agrobacterium. Next transformed callus was obtained by culturing the infected embryos on solid medium containing glyphosphate which inhibits the growth of non-transformed cells. Transformed callus was then able to be regenerated into plants using standard methods.

Levels of HXP4 and NaD1 expression in PCR positive plants were determined, for example, by ELISA screening. Plants expressing HXP4 or NaD1 at >10 ppm were assessed for increased resistance to Colletotrichum graminicola using the bioassay described in the Methods.

Results

Plants expressing HXP4 at >10 ppm showed a 26% reduction in lesion area when compared to plants transformed with an empty vector. Plants expressing NaD1 at >10 ppm showed no reduction in lesion area compared to the empty vector control (Table 8).

Example 8 Production of Transgenic Soybean Plants Expressing HXP4

Transgenic soybean plants expressing HXP4 are produced by Agrobacterium-mediated transformation or by particle bombardment or other standard protocols such as those described in U.S. Pat. No. 7,589,176; U.S. Pat. No. 7,528,293; U.S. Pat. No. 7,785,828.

Regenerated soybean plants which are PCR positive for HXP4 are assessed for levels of HXP4 expression e.g. by ELISA screening. Fertile transgenic plants may be assessed for gene copy number and selected lines are tested for resistance to soybean fungal pathogens in glasshouse bioassays.

Lines exhibiting increased resistance to soybean fungal and rust and insect pathogens are then assessed in field trials in infected soil and in trials where the soybean plants are artificially infected with the target fungal, insect or rust pathogens.

Example 9 Production of Transgenic Wheat Expressing HXP4

Transgenic wheat plants expressing HXP4 are produced by Agrobacterium-mediated transformation or by particle bombardment or other standard protocols such as those described in U.S. Pat. No. 7,785,828. Regenerated wheat plants which are PCR positive for HXP4 are assessed for levels of HXP4 expression e.g. by ELISA screening. Fertile transgenic plants may be assessed for gene copy number and selected lines are tested for resistance to wheat fungal pathogens in glasshouse bioassays.

Lines exhibiting increased resistance to wheat fungal pathogens are then assessed in field trials in infected soil and in trials where the wheat plants are artificially infected with the target fungal pathogens.

Example 10 Activity of Modified NaD1 Against the Human Fungal Pathogen Aspergillus niger

Recombinant NaD1 and the loop variant HXP4 were expressed in the P. pastoris expression system and purified as described in the methods. The anti-fungal activity of the peptides against Aspergillus niger was assessed as described above.

Results

FIG. 12 illustrates the relative anti-fungal activity of the loop variant HXP4 compared to NaD1 against A. niger. At 13 ppm, HXP4 inhibited the growth of A. niger by 20.6% more than NaD1. This can be expressed as HXP4 having greater than 112% of NaD1. At 26 ppm and 53 ppm, HXP4 inhibited growth by at least 10% more than NaD1.

Example 11 Activity of Modified NaD1 Against Cryptococcus Spp.

Recombinant NaD1 and the loop variant HXP4 were expressed in the P. pastoris expression system and purified as described in the methods. The anti-fungal activity of the peptides against two strains of Cryptococcus neoformans and one strain of C. gattii was assessed as described above.

Results

FIG. 13A illustrates the relative anti-fungal activity of the loop variant HXP4 compared to NaD1 against Cryptococcus neoformans (C1065). At 13 ppm, HXP4 completely inhibited growth of the yeast while NaD1 only inhibited ˜16.7%. Hence, HXP4 had more than 596% of the activity of NaD1. Neither protein showed significant activity at 6.5 ppm. FIG. 13B illustrates the relative anti-fungal activity of NaD1 and HXP4 against a second strain of C. neoformans (C2067). At 6.5 ppm, HXP4 inhibited growth by more than 80% while NaD1 only inhibited growth by less than 4%. Against C. gatti (FIG. 13C), HXP4 inhibited 10% more growth than NaD1 at 13 ppm and 38% more growth than NaD1 at 6.5 ppm.

Example 12 Modification to the Loop 1B Region of the Class II Solanaceous Defensin, TPP3 as a Backbone

TPP3 (SEQ ID NO: 5) is selected as the Class II solanaceous defensin backbone. This defensin comprises a Loop 1B having the amino acid sequence: QTFPGL (SEQ ID NO:15). The Loop 1B sequence is changed to that of NaD2 (HRFKGP) [SEQ ID NO:29]. The chimeric protein (HXP107) is expressed in the P. pastoris expression system and purified as described in the methods. The anti-fungal activity of the peptide against Fusarium graminearum is assessed as described in Example 1 as well as its anti-insect activity. The amino acid sequence of HXP107 is set forth in SEQ ID NO:85.

Results:

The HXP107 protein retains antifungal activity against Fusarium graminearum (Fgr) with an IC₅₀ of 0.5 μM. This compares favourably with the activity of the parent protein, TPP3, which has an IC₅₀ of 0.2 μM.

Example 13 Modification to the Loop 1B Region of the Class II Solanaceous Defensins, NsD1, C20 and SL549

NsD1 (SEQ ID NO:49), C20 (isolated from Capsicum)(SEQ ID NO:58) and SL549 (isolated from Nicotiana) (SEQ ID NO:59) are selected as the Class II solanaceous defensin backbone. These defensins comprise a Loop 1B having the amino acid sequence: NTFPGI (SEQ ID NO:12), KYFKGL (SEQ ID NO:60) and NTFPGI (SEQ ID NO:12), respectively. One or more of the amino acid residues in loop 1B is/are substituted by another amino acid residue. All six residues may be altered or 1 or 2 or 3 or 4 or 5 of the residues may be changed. This includes a single amino acid substitution or a Loop 1B swap. Examples of changes include the following sequences (together with the source in parentheses):

[SEQ ID NO: 29] HRFKGP (NaD2); [SEQ ID NO: 30] QHHSFP (Zea2); [SEQ ID NO: 31] DTYRGV (PsD1); [SEQ ID NO: 32] PTWEGI (PsD2); [SEQ ID NO: 33] DKYRGP (MsDeF1(; [SEQ ID NO: 34] KTFKGI (SoD2); [SEQ ID NO: 35] KTWSGN (DmAMP1); [SEQ ID NO: 36] EGWXGK (VrD1); [SEQ ID NO: 37] GTWSGV (RsAFP2); and [SEQ ID NO: 38] AGFKGP (g1-H).

In another embodiment, the Loop 1B is substituted by a sequence selected from SEQ ID NO:67 to 79.

Recombinant loop variants are expressed in the P. pastoris expression system and purified as described in the methods. The anti-fungal activity of the peptides against fungal pathogens such as Fusarium graminearum, Fusarium oxysporum, Colletotrichum graminicola and Fusarium verticilloides is assessed as described in Example 1.

Example 14 Synergy of HXP4 with Protease Inhibitors Against Fusarium graminearum and Colletotrichum graminicola

DNA encoding the mature domain of the barley type-I inhibitor CI-1B (SEQ ID NO:63), the Nicotiana alata type I inhibitor NaPin1A, the tomato cystatin SlCys9 (SEQ ID NO:64), the rice cystatin Os1a (SEQ ID NO:65), and the barley cystatin HvCPI6 (SEQ ID NO:66) was obtained from Genscript. Inserts were excised from the pUC57 vector using Sac II and Sac I, extracted from agarose gels using the Perfectprep kit (Eppendorf) and ligated into pHUE which was then used to transform TOP10 E. coli cells. Plasmid DNA was isolated and then used to transform E. coli Rosetta-Gami B cells.

Single colonies of E. coli Rosetta-Gami B were used to inoculate 2YT media (10 mL, 16 g/L tryptone, 10 g/L yeast extract, 5 g/L NaCl) containing ampicillin (0.1 mg/mL), chloramphenicol (0.34 mg/mL), tetracycline (0.1 mg/mL) and kanamycin (0.05 mg/mL) and grown overnight with shaking at 37° C. This culture was used to inoculate 2YT media (500 mL) containing ampicillin (0.1 mg/mL), chloramphenicol (0.34 mg/mL), tetracycline (0.1 mg/mL) and kanamycin (0.05 mg/mL) which was then grown for 4 h to an optical density (600 nm) of ˜1.0. IPTG was then added (0.5 mM final concentration) and the culture grown for a further 16 h at 16° C. Cells were harvested by centrifugation (4,000 g at 4° C. for 20 min), resuspended in native lysis buffer (20 mL per litre cell culture, 50 mM NaH₂PO₄, 300 mM NaCl, 10 mM imidazole, pH 8.0) and frozen at −80° C. Cells were then thawed and treated with lysozyme (5 mg per 25 mL resuspended cells) for 20 min at 4° C. DNase I (125 uL, 2 mg/mL in 20% v/v glycerol, 75 mM NaCl) and MgCl₂ (125 uL, 1 M) were then added and the samples incubated at room temperature for 40 min on a rocking platform. The samples were then sonicated for 2×30 s on ice (80% w/v power, Branson sonifier 450) and centrifuged (20,000 g at 4° C. for 30 min). The hexahistidine-tagged ubiquitin-fusion proteins (His6-Ub-NaCys1,2,3) were then purified from the protein extracts by immobilized metal affinity chromatography (IMAC) under native conditions using Ni-NTA resin (1.5 mL to ˜25 mL native protein extract, Qiagen) according to the manufacturer's instructions. Recombinant proteins were eluted using elution buffer (250 mM imidazole, 200 mM NaCl, 50 mM NaH₂PO₄, pH 8.0). The imidazole was removed by applying the eluted protein to a prepacked Sephadex G50 gel filtration column (PD-10, Amersham) equilibrated with 50 mM Tris.Cl, 100 mM NaCl, pH 8.0.

The hexahistidine-tagged ubiquitin was cleaved from the recombinant proteins using the deubiquitylating enzyme 6H.Usp2-cc (Catanzariti et al. (2004), Protein Science 13:1331-1339). The cleaved tag was removed by another round of IMAC with the deubiquitylated protease inhibitors as the unbound protein. This was then further purified by reversed-phase HPLC.

Recombinant CI-1B, SlCys9 and Os1a were prepared as stock solutions (20 μM) in H₂O. Trypsin inhibitor type I-P from bovine pancreas (Anderson and Kingston (1983), Proc. Natl. Acad. USA 80:6838-6842) was purchased from Sigma (T0256) and diluted to a concentration of 20 μM in H₂0.

The inhibitory effects of HXP4 and NaD1 in combination with serine or cysteine proteinase inhibitors on the growth of Fusarium graminearum, or Colletotrichum gramincola was measured essentially as described by Broekaert et al, supra 1990. Spores were isolated from sporulating cultures growing on synthetic nutrient poor agar (SNPB, Fusarium graminearum) or V8 agar (Colletotrichum graminicola) and counted using a hemocytometer.

Antifungal assays were conducted in 96 well microtiter trays essentially as described in Example 1. Wells were loaded with 10 μL of filter sterilized (0.22 μm syringe filter, Millipore) NaD1 (2.5 μM), HXP4 (2.5 μM) or water, along with 10 μL of filter sterilized (0.22 μm syringe filter, Millipore) proteinase inhibitor or water and 80 μL 5×10⁴ spores/mL in ½ strength PDB. The plates were incubated at 25° C. Fungal growth was assayed by measuring optical density at 595 nm (A₅₉₅) using a microtitre plate reader (SpectraMax Pro M2; Molecular Devices). Each test was performed in quadruplicate.

Results

When tested at the same concentration, HXP4 had a greater synergistic effect with protease inhibitors than NaD1 against Fusarium graminearum. HXP4 was also synergistic with protease inhibitors against Colletotrichum graminicola. Synergy calculations are presented in Tables 6 and 7 wherein Ee is the expected effect from the additive response according to Limpel's formula (Richer et al. Pestic Sci 19:309-315) expressed as percent inhibition and Io is the percent inhibition observed. Synergy, that is, Io values higher than Ee values was obtained with all four protease inhibitors.

Example 15 In Planta Synergy of HXP 4 with HvCP16 Against Fusarium graminearum

Transgenic corn plants expressing HXP4, HvCPI6 or HXP4+HvCPI6 are created using the method described in Example 7 and are assessed for increased resistance to Fusarium graminearum using the bioassay described in the Methods.

FIG. 15 provides the HvCPI6 construct for expression in corn and FIG. 16 provides the HXP4+HvCP16 construct for expression in corn.

Results

Plants expressing HXP4 alone or HvCPI6 alone show no reduction in lesion area compared to plants transformed with an empty vector. Plants expressing HXP4+HvCPI6 show a 45% reduction in lesion area compared to the empty vector control (Table 9).

Example 16 Effects of HXP4 on Asian Soybean Rust

NaD1 was isolated from flowers of Nicotiana alata and the loop variant HXP4 was expressed in the P. pastoris expression system and purified as described in the methods. The effects of HXP4 on Asian soybean rust (Phakopsora pachirhizi) was tested and compared to NaD1. Phakopsora pachirhizi urediospores were grown on cellophane that was placed on an agar droplet in the presence or absence of the peptides at 100, 10, 1 and 0.1 ppm in water. Germination, appressorium formation, and formation of post-appressorial structures were evaluated using microscopy at 24 h and 48 h. Three membranes were examined per treatment and fifty isolated germlings were evaluated per membrane.

Results

The effect on germination (24 hours; FIG. 14A), appresorium formation (24 hours; FIG. 14B) and formation of post-appresorium structure (48 hours; FIG. 14C) were all examined. At 10 ppm, HXP4 inhibited germination 62% more effectively than NaD1 while appresorium formation and formation of post-appresorium structures were inhibited by 65% and 59% more than NaD1, respectively.

Example 17 High-Throughput Screening to Identify Novel Loop 1B Sequences

Site directed mutagenesis of NaD1 was carried out using the Phusion (Registered Trademark) site-directed mutagenesis kit (Finnzymes). Degenerate oligonucleotide primers phosphorylated at the 5′ end were designed to incorporate the random six amino acid mutation of Loop 1B.

The pHUE system was used for expression of a library of loop 1B variants. Expression and purification was modified slightly from the method described in Example 14 to enable expression in 48-well plates and purification in 96-well filter plates. The entire template plasmid (pHUE-NaD1) was amplified in a PCR reaction of 35 cycles with an annealing temperature of 66° C., 30 sec. The linear PCR product was then circularized using T4 DNA Ligase overnight at 16° C. and transformed into electro competent Rosetta-Gami B (DE3) cells according to the manufacturer's instructions. The recovered cells were plated onto 2YT agar containing ampicillin (0.1 mg/mL), chloramphenicol (0.34 mg/mL), tetracycline (0.1 mg/mL) and kanamycin (0.015 mg/mL) and incubated at 37° C. overnight.

Single colonies were used to inoculate 150 μL of 2YT containing ampicillin (0.1 mg/mL), chloramphenicol (0.34 mg/mL), tetracycline (0.1 mg/mL) and kanamycin (0.015 mg/mL) in 96-well plates. Rosetta-Gami B (DE3) transformed with pHUE-NaD1 was included as a positive control. Plates were incubated overnight at 37° C. with constant shaking at 70% humidity. Fifty microliters of each well was transferred to 2.5 mL of 2YT antibiotics and expression and purification was performed as described in Example 13.

Proteins were tested for activity against Colletotrichum graminicola. Fifteen microliters of protein solution was added to 105 μL of spore solution to give a final concentration of 2×10⁴ spores/mL in ½×Potato Dextrose Broth containing 0.5 mM CaCl₂, 25 mM KCl. The plates were incubated at 25° C. and fungal growth was assayed after 40 h by measuring optical density at 595 nm using a microtitre plate reader (SpectraMax Pro M5e; Molecular Devices). Proteins that inhibited fungal growth equal to or greater than the NaD1 control were identified by sequencing the plasmid DNA of the bacterial colony used for expression. A single colony identified in the screen was found to have a loop 1B sequence identical to that of NaD1. Several colonies were selected for large scale purification and testing. Proteins were expressed and as described in Example 14 and tested for activity against Fusarium graminicola and Colletotrichum graminicola as described in Example 1. Loop 1B sequences identified are listed in Table 10.

TABLE 6 Synergistic effect of HXP4 vs NaD1 in combination with proteinase inhibitors against Fgr Protease HXP4 NaD1 inhibitor Ee Io Ee Io CI-1B 12.1 81.1 17.1 27.3 SICys9 0.0 86.0 0.0 37.6 Oc1a 0.0 90.7 0.0 11.3 BTPI 2.0 81.0 2.0 5.0

TABLE 7 Synergistic effect of HXP4 in combination with proteinase inhibitors against Cgr Protease HXP4 inhibitor Ee Io BPTI 16.7 97.1 NaPin1A 11.8 69.3 HvCPI6 13.8 100.0 SICys9 15.4 94.9

TABLE 8 Protection of transgenic corn plants expressing HXP4 or NaD1 against Cgr Percent inhibition relative Protein of empty vector control P-value HXP4 26 0.029 NaD1 0 0.997

TABLE 9 Protection of transgenic corn plants expression HXP4 in combination with HvCPI6 against Fgr Percent inhibition relative Protein of empty vector control P-value HXP4 0 0.183 HvCPI6 0 0.697 HXP4 + HvCPI6 45 <0.001

TABLE 10 Loop 1B sequences from proteins that inhibit the growth of Colletotrichum graminicola LSAKMV (SEQ ID NO: 88) LSFKGT (SEQ ID NO: 67) LVFGGM (SEQ ID NO: 68) YNPVGL (SEQ ID NO: 69) LFWEKS (SEQ ID NO: 70) SPFVGP (SEQ ID NO: 71) FINRDW (SEQ ID NO: 89) SIIASA (SEQ ID NO: 72) IKAPGW (SEQ ID NO: 73) LTLSNH (SEQ ID NO: 74) LISFYP (SEQ ID NO: 75) LVSFPG (SEQ ID NO: 90) ALFAGE (SEQ ID NO: 76) FLYREK (SEQ ID NO: 77) FIFRME (SEQ ID NO: 78) HAFQKG (SEQ ID NO: 79)

Those skilled in the art will appreciate that the disclosure described herein is susceptible to variations and modifications other than those specifically described. It is to be understood that the disclosure includes all such variations and modifications. The disclosure also includes all of the steps, features, compositions and compounds referred to or indicated in this specification, individually or collectively, and any and all combinations of any two or more of these steps or features.

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1. An isolated polynucleotide encoding an artificially modified solanaceous Class II defensin polypeptide, wherein the polypeptide comprises: the amino acid sequence of NaD1 set forth in SEQ ID NO: 2, or an amino acid sequence having at least 70% identity to SEQ ID NO: 2 and at least 70% identity to the C-terminal end of NaD1 set forth in SEQ ID NO: 52; and wherein the Loop 1B amino acid sequence at positions 8-13 of SEQ ID NO: 2, or the Loop 1B amino acid sequence at positions equivalent to 8-13 of an amino acid sequence having at least 70% identity to SEQ ID NO:2 and at least 70% identity to SEQ ID NO: 52 after optimal alignment to SEQ ID NO: 2 is replaced by an exogenous Loop 1B amino acid sequence selected from the group consisting of SEQ ID NOs: 29 through 38 and 67 through
 79. 2. The isolated polynucleotide encoding the modified solanaceous Class II defensin polypeptide of claim 1, wherein the Loop 1B amino acid sequence is replaced by an exogenous Loop 1B amino acid sequence selected from the group consisting of SEQ ID NOs:29 through
 38. 3. The isolated polynucleotide encoding the modified solanaceous Class II defensin polypeptide of claim 1, wherein the Loop 1B amino acid sequence is replaced by an exogenous Loop 1B amino acid sequence selected from the group consisting of SEQ ID NOs:67 through
 79. 4. The isolated polynucleotide encoding the modified solanaceous Class II defensin polypeptide of claim 1, wherein the Loop 1B amino acid sequence is replaced by the endogenous Loop 1B amino acid sequence of SEQ ID NO:29.
 5. The isolated polynucleotide encoding the modified solanaceous Class II defensin polypeptide of claim 1 which polypeptide is at least 90% amino acid sequence identity to a polypeptide selected from HXP4 (SEQ ID NO:39), HXP34 (SEQ ID NO:40) and HXP35 (SEQ ID NO:41).
 6. The isolated polynucleotide encoding the modified solanaceous Class II defensin polypeptide of claim 5 wherein the polypeptide is selected from the group consisting of HXP4 (SEQ ID NO:39), HXP34 (SEQ ID NO:40) and HXP35 (SEQ ID NO:41).
 7. The isolated polynucleotide encoding the modified solanaceous Class II defensin polypeptide of claim 1 wherein the polypeptide comprises the amino acid sequence of NaD1 set forth in SEQ ID NO: 2; wherein the Loop 1B amino acid sequence at positions 8-13 of SEQ ID NO: 2 is replaced by an exogenous Loop 1B amino acid sequence selected from the group consisting of SEQ ID NOs: 29 through 38, and 67 through
 79. 8. The isolated polynucleotide encoding the modified solanaceous Class II defensin polypeptide of claim 7, wherein the Loop 1B amino acid sequence is replaced by an exogenous Loop 1B amino acid sequence selected from the group consisting of SEQ ID NOs: 29 through
 38. 9. The isolated polynucleotide encoding the modified solanaceous Class II defensin polypeptide of claim 7, wherein the Loop 1B amino acid sequence is replaced by an exogenous Loop 1B amino acid sequence selected from the group consisting of SEQ ID NOs: 67 through
 79. 10. The isolated polynucleotide encoding the modified solanaceous Class II defensin polypeptide of claim 7, wherein the Loop 1B amino acid sequence is replaced by the exogenous Loop 1B amino acid sequence SEQ ID NO:
 29. 11. A genetic construct comprising the polynucleotide of claim
 1. 12. A genetically modified plant comprising the polynucleotide of claim 1 or genetic construct of claim 11 or progeny of said plant wherein the plant or its progeny expresses the polynucleotide to produce the artificially modified solanaceous Class II defensin polypeptide.
 13. The genetically modified plant of claim 12, selected from the group consisting of corn, soybean, cotton, sorghum, wheat, barley, maize, canola, abaca, alfalfa, almond, apple, asparagus, banana, bean-phaseolus, blackberry, broad bean, cashew, cassava, chickpea, citrus, coconut, coffee, fig, flax, grapes, groundnut, hemp, lavender, mushroom, olive, onion, pea, peanut, pear, pearl millet, potato, rapeseed, ryegrass, strawberry, sugarbeet, sugarcane, sunflower, sweetpotato, taro, tea, tobacco, tomato, triticale, truffle and yam.
 14. A method for generating a genetically modified plant or its progeny which exhibits anti-fungal activity as a result of the genetic modification, the method comprising creating a plant which comprises cells which express the nucleic acid encoding the polypeptide of claim 1, the level of expression in the plant or its progeny sufficient for the modified defensin to exhibit a protective effect against a plant fungal pathogen. 